* [PATCH v7 10/12] ima: Add support for flushing the hash table when staging measurements
From: Roberto Sassu @ 2026-06-05 17:22 UTC (permalink / raw)
To: corbet, skhan, zohar, dmitry.kasatkin, eric.snowberg, paul,
jmorris, serge
Cc: linux-doc, linux-kernel, linux-integrity, linux-security-module,
gregorylumen, chenste, nramas, Roberto Sassu
In-Reply-To: <20260605172236.2042045-1-roberto.sassu@huaweicloud.com>
From: Roberto Sassu <roberto.sassu@huawei.com>
During staging and delete, measurements are not completely deallocated.
Their entry digest portion is kept and is still reachable with the hash
table to detect duplicate records. If the number of records is significant,
this reduces the memory saving benefit of staging.
Some users might be interested in achieving the best memory saving (the
measurements are completely deallocated) at the cost of having duplicate
records across the staged measurement lists. Duplicate records are still
avoided within the current measurement list.
Introduce the new kernel option ima_flush_htable to decide whether or not
the digests of staged measurement records are flushed from the hash table,
when they are deleted, to achieve the maximum memory saving.
When the option is enabled, replace the old hash table with a new one,
by calling ima_alloc_replace_htable(), and completely delete the
measurements records.
Note: This code derives from the Alt-IMA Huawei project, whose license is
GPL-2.0 OR MIT.
Link: https://github.com/linux-integrity/linux/issues/1
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
.../admin-guide/kernel-parameters.txt | 6 +++
security/integrity/ima/ima_queue.c | 41 ++++++++++++++++---
2 files changed, 41 insertions(+), 6 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 4d0f545fb3ec..aad318803f82 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2343,6 +2343,12 @@ Kernel parameters
Use the canonical format for the binary runtime
measurements, instead of host native format.
+ ima_flush_htable [IMA]
+ Flush the IMA hash table when deleting all the
+ staged measurement records, to achieve maximum
+ memory saving at the cost of having duplicate
+ records across the staged measurement lists.
+
ima_hash= [IMA]
Format: { md5 | sha1 | rmd160 | sha256 | sha384
| sha512 | ... }
diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
index cdc21e1b929b..df1e81ea7a36 100644
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -22,6 +22,20 @@
#define AUDIT_CAUSE_LEN_MAX 32
+static bool ima_flush_htable;
+
+static int __init ima_flush_htable_setup(char *str)
+{
+ if (IS_ENABLED(CONFIG_IMA_DISABLE_HTABLE)) {
+ pr_warn("Hash table not enabled, ignoring request to flush\n");
+ return 1;
+ }
+
+ ima_flush_htable = true;
+ return 1;
+}
+__setup("ima_flush_htable", ima_flush_htable_setup);
+
/* pre-allocated array of tpm_digest structures to extend a PCR */
static struct tpm_digest *digests;
@@ -332,7 +346,7 @@ int ima_queue_stage(void)
return ret;
}
-static void ima_queue_delete(struct list_head *head);
+static void ima_queue_delete(struct list_head *head, bool flush_htable);
/**
* ima_queue_staged_delete_all - Delete staged measurements
@@ -350,6 +364,7 @@ static void ima_queue_delete(struct list_head *head);
*/
int ima_queue_staged_delete_all(void)
{
+ struct hlist_head *old_queue = NULL;
LIST_HEAD(ima_measurements_trim);
mutex_lock(&ima_extend_list_mutex);
@@ -371,21 +386,35 @@ int ima_queue_staged_delete_all(void)
if (IS_ENABLED(CONFIG_IMA_KEXEC))
binary_runtime_size[BINARY_STAGED] = 0;
+ if (ima_flush_htable) {
+ old_queue = ima_alloc_replace_htable();
+ if (IS_ERR(old_queue)) {
+ mutex_unlock(&ima_extend_list_mutex);
+ return PTR_ERR(old_queue);
+ }
+ }
+
mutex_unlock(&ima_extend_list_mutex);
- ima_queue_delete(&ima_measurements_trim);
+ if (ima_flush_htable) {
+ synchronize_rcu();
+ kfree(old_queue);
+ }
+
+ ima_queue_delete(&ima_measurements_trim, ima_flush_htable);
return 0;
}
/**
* ima_queue_delete - Delete measurements
* @head: List head measurements are deleted from
+ * @flush_htable: Whether or not the hash table is being flushed
*
* Delete the measurements from the passed list head completely if the
- * hash table is not enabled, or partially (only the template data), if the
- * hash table is used.
+ * hash table is not enabled or is being flushed, or partially (only the
+ * template data), if the hash table is used.
*/
-static void ima_queue_delete(struct list_head *head)
+static void ima_queue_delete(struct list_head *head, bool flush_htable)
{
struct ima_queue_entry *qe, *qe_tmp;
unsigned int i;
@@ -407,7 +436,7 @@ static void ima_queue_delete(struct list_head *head)
list_del(&qe->later);
/* No leak if condition is false, referenced by ima_htable. */
- if (IS_ENABLED(CONFIG_IMA_DISABLE_HTABLE)) {
+ if (IS_ENABLED(CONFIG_IMA_DISABLE_HTABLE) || flush_htable) {
kfree(qe->entry->digests);
kfree(qe->entry);
kfree(qe);
--
2.43.0
^ permalink raw reply related
* [PATCH v7 09/12] ima: Add support for staging measurements with prompt
From: Roberto Sassu @ 2026-06-05 17:22 UTC (permalink / raw)
To: corbet, skhan, zohar, dmitry.kasatkin, eric.snowberg, paul,
jmorris, serge
Cc: linux-doc, linux-kernel, linux-integrity, linux-security-module,
gregorylumen, chenste, nramas, Roberto Sassu, Stefan Berger
In-Reply-To: <20260605172236.2042045-1-roberto.sassu@huaweicloud.com>
From: Roberto Sassu <roberto.sassu@huawei.com>
Introduce the ability of staging the IMA measurement list and deleting them
with a prompt.
Staging means moving the current measurement list records to a separate
location, and allowing users to read and delete it. This causes the current
measurement list to be emptied (since records were moved) and new
measurements to be added on the empty list. Staging can be done only once
at a time. In the event of kexec(), staging is aborted and staged records
will be carried over to the new kernel.
Introduce ascii_runtime_measurements_<algo>_staged and
binary_runtime_measurements_<algo>_staged interfaces to access and delete
the measurements.
Use 'echo A > <IMA _staged interface>' and
'echo D > <IMA _staged interface>' to respectively stage and delete the
entire measurements list. Locking of these interfaces is also mediated with
a call to _ima_measurements_open() and with ima_measurements_release().
Implement the staging functionality by introducing the new global
measurements list ima_measurements_staged, and ima_queue_stage() and
ima_queue_staged_delete_all() to respectively move measurements from the
current measurements list to the staged one, and to move staged
measurements to the ima_measurements_trim list for deletion. Introduce
ima_queue_delete() to delete the measurements.
Staging is forbidden after measurement is suspended, and between staging
and deleting, so that walking the staged and current measurements list can
be done locklessly in ima_dump_measurement_list(). Strict ordering of
suspending and dumping is enforced by two reboot notifiers with different
priority. Refusing to delete staged measurements also signals to user space
that those measurements are already carried over to the secondary kernel,
so that it does not save them twice.
Finally, introduce the BINARY_STAGED and BINARY_FULL binary measurements
list types, to maintain the counters and the binary size of staged
measurements and the full measurements list (including records that were
staged). BINARY still represents the current binary measurements list.
Use the binary size for the BINARY + BINARY_STAGED types in
ima_add_kexec_buffer(), since both measurements list types are copied to
the secondary kernel during kexec. Use BINARY_FULL in
ima_measure_kexec_event(), to generate a critical data record.
It should be noted that the BINARY_FULL counter is not passed through
kexec. Thus, the number of records included in the kexec critical data
records refers to the records since the critical data records generated
from the previous kexec event.
Note: This code derives from the Alt-IMA Huawei project, whose license is
GPL-2.0 OR MIT.
Link: https://github.com/linux-integrity/linux/issues/1
Suggested-by: Gregory Lumen <gregorylumen@linux.microsoft.com> (staging revert)
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Tested-by: Stefan Berger <stefanb@linux.ibm.com>
---
security/integrity/ima/Kconfig | 12 ++
security/integrity/ima/ima.h | 7 +-
security/integrity/ima/ima_fs.c | 174 ++++++++++++++++++++++++++---
security/integrity/ima/ima_kexec.c | 20 +++-
security/integrity/ima/ima_queue.c | 140 ++++++++++++++++++++++-
5 files changed, 333 insertions(+), 20 deletions(-)
diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 862fbee2b174..02436670f746 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -332,4 +332,16 @@ config IMA_KEXEC_EXTRA_MEMORY_KB
If set to the default value of 0, an extra half page of memory for those
additional measurements will be allocated.
+config IMA_STAGING
+ bool "Support for staging the measurements list"
+ default n
+ help
+ Add support for staging the measurements list.
+
+ It allows user space to stage the measurements list for deletion and
+ to delete the staged measurements after confirmation.
+
+ On kexec, staging is aborted and any staged measurement records are
+ copied to the secondary kernel.
+
endif
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index c00c133a140f..3892d2a6c2e2 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -30,9 +30,11 @@ enum tpm_pcrs { TPM_PCR0 = 0, TPM_PCR8 = 8, TPM_PCR10 = 10 };
/*
* BINARY: current binary measurements list
+ * BINARY_STAGED: staged binary measurements list
+ * BINARY_FULL: binary measurements list since IMA init (lost after kexec)
*/
enum binary_lists {
- BINARY, BINARY__LAST
+ BINARY, BINARY_STAGED, BINARY_FULL, BINARY__LAST
};
/* digest size for IMA, fits SHA1 or MD5 */
@@ -125,6 +127,7 @@ struct ima_queue_entry {
struct ima_template_entry *entry;
};
extern struct list_head ima_measurements; /* list of all measurements */
+extern struct list_head ima_measurements_staged; /* list of staged meas. */
/* Some details preceding the binary serialized measurement list */
struct ima_kexec_hdr {
@@ -315,6 +318,8 @@ struct ima_template_desc *ima_template_desc_current(void);
struct ima_template_desc *ima_template_desc_buf(void);
struct ima_template_desc *lookup_template_desc(const char *name);
bool ima_template_has_modsig(const struct ima_template_desc *ima_template);
+int ima_queue_stage(void);
+int ima_queue_staged_delete_all(void);
int ima_restore_measurement_entry(struct ima_template_entry *entry);
int ima_restore_measurement_list(loff_t bufsize, void *buf);
int ima_measurements_show(struct seq_file *m, void *v);
diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index f6ecee2d7699..96d7503a605b 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -24,6 +24,13 @@
#include "ima.h"
+/*
+ * Requests:
+ * 'A\n': stage the entire measurements list
+ * 'D\n': delete all staged measurements
+ */
+#define STAGED_REQ_LENGTH 21
+
static DEFINE_MUTEX(ima_write_mutex);
static DEFINE_MUTEX(ima_measure_mutex);
static long ima_measure_users;
@@ -99,6 +106,11 @@ static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
return _ima_measurements_start(m, pos, &ima_measurements);
}
+static void *ima_measurements_staged_start(struct seq_file *m, loff_t *pos)
+{
+ return _ima_measurements_start(m, pos, &ima_measurements_staged);
+}
+
static void *_ima_measurements_next(struct seq_file *m, void *v, loff_t *pos,
struct list_head *head)
{
@@ -120,6 +132,12 @@ static void *ima_measurements_next(struct seq_file *m, void *v, loff_t *pos)
return _ima_measurements_next(m, v, pos, &ima_measurements);
}
+static void *ima_measurements_staged_next(struct seq_file *m, void *v,
+ loff_t *pos)
+{
+ return _ima_measurements_next(m, v, pos, &ima_measurements_staged);
+}
+
static void ima_measurements_stop(struct seq_file *m, void *v)
{
}
@@ -213,6 +231,13 @@ static const struct seq_operations ima_measurments_seqops = {
.show = ima_measurements_show
};
+static const struct seq_operations ima_measurments_staged_seqops = {
+ .start = ima_measurements_staged_start,
+ .next = ima_measurements_staged_next,
+ .stop = ima_measurements_stop,
+ .show = ima_measurements_show
+};
+
static int ima_measure_lock(bool write)
{
mutex_lock(&ima_measure_mutex);
@@ -307,6 +332,60 @@ static int ima_measurements_release(struct inode *inode, struct file *file)
return ret;
}
+static int ima_measurements_staged_open(struct inode *inode, struct file *file)
+{
+ return _ima_measurements_open(inode, file,
+ &ima_measurments_staged_seqops);
+}
+
+static ssize_t _ima_measurements_write(struct file *file,
+ const char __user *buf, size_t datalen,
+ loff_t *ppos, bool staged_interface)
+{
+ char req[STAGED_REQ_LENGTH];
+ int ret;
+
+ if (datalen < 2 || datalen > STAGED_REQ_LENGTH)
+ return -EINVAL;
+
+ if (copy_from_user(req, buf, datalen) != 0)
+ return -EFAULT;
+
+ if (req[datalen - 1] != '\n')
+ return -EINVAL;
+
+ req[datalen - 1] = '\0';
+
+ switch (req[0]) {
+ case 'A':
+ if (datalen != 2 || !staged_interface)
+ return -EINVAL;
+
+ ret = ima_queue_stage();
+ break;
+ case 'D':
+ if (datalen != 2 || !staged_interface)
+ return -EINVAL;
+
+ ret = ima_queue_staged_delete_all();
+ break;
+ default:
+ ret = -EINVAL;
+ }
+
+ if (ret < 0)
+ return ret;
+
+ return datalen;
+}
+
+static ssize_t ima_measurements_staged_write(struct file *file,
+ const char __user *buf,
+ size_t datalen, loff_t *ppos)
+{
+ return _ima_measurements_write(file, buf, datalen, ppos, true);
+}
+
static const struct file_operations ima_measurements_ops = {
.open = ima_measurements_open,
.read = seq_read,
@@ -314,6 +393,14 @@ static const struct file_operations ima_measurements_ops = {
.release = ima_measurements_release,
};
+static const struct file_operations ima_measurements_staged_ops = {
+ .open = ima_measurements_staged_open,
+ .read = seq_read,
+ .write = ima_measurements_staged_write,
+ .llseek = seq_lseek,
+ .release = ima_measurements_release,
+};
+
void ima_print_digest(struct seq_file *m, u8 *digest, u32 size)
{
u32 i;
@@ -387,6 +474,28 @@ static const struct file_operations ima_ascii_measurements_ops = {
.release = ima_measurements_release,
};
+static const struct seq_operations ima_ascii_measurements_staged_seqops = {
+ .start = ima_measurements_staged_start,
+ .next = ima_measurements_staged_next,
+ .stop = ima_measurements_stop,
+ .show = ima_ascii_measurements_show
+};
+
+static int ima_ascii_measurements_staged_open(struct inode *inode,
+ struct file *file)
+{
+ return _ima_measurements_open(inode, file,
+ &ima_ascii_measurements_staged_seqops);
+}
+
+static const struct file_operations ima_ascii_measurements_staged_ops = {
+ .open = ima_ascii_measurements_staged_open,
+ .read = seq_read,
+ .write = ima_measurements_staged_write,
+ .llseek = seq_lseek,
+ .release = ima_measurements_release,
+};
+
static ssize_t ima_read_policy(char *path)
{
void *data = NULL;
@@ -490,10 +599,21 @@ static const struct seq_operations ima_policy_seqops = {
};
#endif
-static int __init create_securityfs_measurement_lists(void)
+static int __init create_securityfs_measurement_lists(bool staging)
{
+ const struct file_operations *ascii_ops = &ima_ascii_measurements_ops;
+ const struct file_operations *binary_ops = &ima_measurements_ops;
+ umode_t permissions = (S_IRUSR | S_IRGRP);
+ const char *file_suffix = "";
int count = NR_BANKS(ima_tpm_chip);
+ if (staging) {
+ ascii_ops = &ima_ascii_measurements_staged_ops;
+ binary_ops = &ima_measurements_staged_ops;
+ permissions |= (S_IWUSR | S_IWGRP);
+ file_suffix = "_staged";
+ }
+
if (ima_sha1_idx >= NR_BANKS(ima_tpm_chip))
count++;
@@ -504,29 +624,32 @@ static int __init create_securityfs_measurement_lists(void)
if (algo == HASH_ALGO__LAST)
snprintf(file_name, sizeof(file_name),
- "ascii_runtime_measurements_tpm_alg_%x",
- ima_tpm_chip->allocated_banks[i].alg_id);
+ "ascii_runtime_measurements_tpm_alg_%x%s",
+ ima_tpm_chip->allocated_banks[i].alg_id,
+ file_suffix);
else
snprintf(file_name, sizeof(file_name),
- "ascii_runtime_measurements_%s",
- hash_algo_name[algo]);
- dentry = securityfs_create_file(file_name, S_IRUSR | S_IRGRP,
+ "ascii_runtime_measurements_%s%s",
+ hash_algo_name[algo], file_suffix);
+ dentry = securityfs_create_file(file_name, permissions,
ima_dir, (void *)(uintptr_t)i,
- &ima_ascii_measurements_ops);
+ ascii_ops);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
if (algo == HASH_ALGO__LAST)
snprintf(file_name, sizeof(file_name),
- "binary_runtime_measurements_tpm_alg_%x",
- ima_tpm_chip->allocated_banks[i].alg_id);
+ "binary_runtime_measurements_tpm_alg_%x%s",
+ ima_tpm_chip->allocated_banks[i].alg_id,
+ file_suffix);
else
snprintf(file_name, sizeof(file_name),
- "binary_runtime_measurements_%s",
- hash_algo_name[algo]);
- dentry = securityfs_create_file(file_name, S_IRUSR | S_IRGRP,
+ "binary_runtime_measurements_%s%s",
+ hash_algo_name[algo], file_suffix);
+
+ dentry = securityfs_create_file(file_name, permissions,
ima_dir, (void *)(uintptr_t)i,
- &ima_measurements_ops);
+ binary_ops);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
}
@@ -534,6 +657,23 @@ static int __init create_securityfs_measurement_lists(void)
return 0;
}
+static int __init create_securityfs_staging_links(void)
+{
+ struct dentry *dentry;
+
+ dentry = securityfs_create_symlink("binary_runtime_measurements_staged",
+ ima_dir, "binary_runtime_measurements_sha1_staged", NULL);
+ if (IS_ERR(dentry))
+ return PTR_ERR(dentry);
+
+ dentry = securityfs_create_symlink("ascii_runtime_measurements_staged",
+ ima_dir, "ascii_runtime_measurements_sha1_staged", NULL);
+ if (IS_ERR(dentry))
+ return PTR_ERR(dentry);
+
+ return 0;
+}
+
/*
* ima_open_policy: sequentialize access to the policy file
*/
@@ -626,7 +766,13 @@ int __init ima_fs_init(void)
goto out;
}
- ret = create_securityfs_measurement_lists();
+ ret = create_securityfs_measurement_lists(false);
+ if (ret == 0 && IS_ENABLED(CONFIG_IMA_STAGING)) {
+ ret = create_securityfs_measurement_lists(true);
+ if (ret == 0)
+ ret = create_securityfs_staging_links();
+ }
+
if (ret != 0)
goto out;
diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index 26d41974429e..0d845693a1f7 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -42,8 +42,8 @@ void ima_measure_kexec_event(const char *event_name)
long len;
int n;
- buf_size = ima_get_binary_runtime_size(BINARY);
- len = atomic_long_read(&ima_num_records[BINARY]);
+ buf_size = ima_get_binary_runtime_size(BINARY_FULL);
+ len = atomic_long_read(&ima_num_records[BINARY_FULL]);
n = scnprintf(ima_kexec_event, IMA_KEXEC_EVENT_LEN,
"kexec_segment_size=%lu;ima_binary_runtime_size=%lu;"
@@ -106,13 +106,24 @@ static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
memset(&khdr, 0, sizeof(khdr));
khdr.version = 1;
- /* This is an append-only list, no need to hold the RCU read lock */
- list_for_each_entry_rcu(qe, &ima_measurements, later, true) {
+ /*
+ * Lockless walks possible due to strict ordering of the reboot
+ * notifiers, suspending measurement before dump, and forbidding
+ * staging/deleting (list mutations) after suspend.
+ */
+ list_for_each_entry(qe, &ima_measurements_staged, later) {
ret = ima_dump_measurement(&khdr, qe);
if (ret < 0)
break;
}
+ list_for_each_entry(qe, &ima_measurements, later) {
+ if (!ret)
+ ret = ima_dump_measurement(&khdr, qe);
+ if (ret < 0)
+ break;
+ }
+
/*
* fill in reserved space with some buffer details
* (eg. version, buffer size, number of measurements)
@@ -167,6 +178,7 @@ void ima_add_kexec_buffer(struct kimage *image)
extra_memory = CONFIG_IMA_KEXEC_EXTRA_MEMORY_KB * 1024;
binary_runtime_size = ima_get_binary_runtime_size(BINARY) +
+ ima_get_binary_runtime_size(BINARY_STAGED) +
extra_memory;
if (binary_runtime_size >= ULONG_MAX - PAGE_SIZE)
diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
index 618694d5c082..cdc21e1b929b 100644
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -26,6 +26,7 @@
static struct tpm_digest *digests;
LIST_HEAD(ima_measurements); /* list of all measurements */
+LIST_HEAD(ima_measurements_staged); /* list of staged measurements */
#ifdef CONFIG_IMA_KEXEC
static unsigned long binary_runtime_size[BINARY__LAST];
#else
@@ -42,7 +43,7 @@ atomic_long_t ima_num_violations = ATOMIC_LONG_INIT(0);
/* key: inode (before secure-hashing a file) */
struct hlist_head __rcu *ima_htable;
-/* mutex protects atomicity of extending measurement list
+/* mutex protects atomicity of extending and staging measurement list
* and extending the TPM PCR aggregate. Since tpm_extend can take
* long (and the tpm driver uses a mutex), we can't use the spinlock.
*/
@@ -171,12 +172,16 @@ static int ima_add_digest_entry(struct ima_template_entry *entry,
lockdep_is_held(&ima_extend_list_mutex));
atomic_long_inc(&ima_num_records[BINARY]);
+ atomic_long_inc(&ima_num_records[BINARY_FULL]);
+
if (update_htable) {
key = ima_hash_key(entry->digests[ima_hash_algo_idx].digest);
hlist_add_head_rcu(&qe->hnext, &htable[key]);
}
ima_update_binary_runtime_size(entry, BINARY);
+ ima_update_binary_runtime_size(entry, BINARY_FULL);
+
return 0;
}
@@ -277,6 +282,139 @@ int ima_add_template_entry(struct ima_template_entry *entry, int violation,
return result;
}
+/**
+ * ima_queue_stage - Stage all measurements
+ *
+ * If the staged measurements list is empty, the current measurements list is
+ * not empty, and measurement is not suspended, move the measurements from the
+ * current list to the staged one, and update the number of records and binary
+ * run-time size accordingly.
+ *
+ * Do not allow staging after measurement is suspended, so that dumping
+ * measurements can be done in a lockless way.
+ *
+ * Return: Zero on success, a negative value otherwise.
+ */
+int ima_queue_stage(void)
+{
+ int ret = 0;
+
+ mutex_lock(&ima_extend_list_mutex);
+ if (!list_empty(&ima_measurements_staged)) {
+ ret = -EEXIST;
+ goto out_unlock;
+ }
+
+ if (list_empty(&ima_measurements)) {
+ ret = -ENOENT;
+ goto out_unlock;
+ }
+
+ if (ima_measurements_suspended) {
+ ret = -EACCES;
+ goto out_unlock;
+ }
+
+ list_replace(&ima_measurements, &ima_measurements_staged);
+ INIT_LIST_HEAD(&ima_measurements);
+
+ atomic_long_set(&ima_num_records[BINARY_STAGED],
+ atomic_long_read(&ima_num_records[BINARY]));
+ atomic_long_set(&ima_num_records[BINARY], 0);
+
+ if (IS_ENABLED(CONFIG_IMA_KEXEC)) {
+ binary_runtime_size[BINARY_STAGED] =
+ binary_runtime_size[BINARY];
+ binary_runtime_size[BINARY] = 0;
+ }
+out_unlock:
+ mutex_unlock(&ima_extend_list_mutex);
+ return ret;
+}
+
+static void ima_queue_delete(struct list_head *head);
+
+/**
+ * ima_queue_staged_delete_all - Delete staged measurements
+ *
+ * Move staged measurements to a temporary list, ima_measurements_trim, update
+ * the number of records and the binary run-time size accordingly. Finally,
+ * delete measurements in the temporary list.
+ *
+ * Refuse to delete staged measurements if measurement is suspended, so that
+ * dump can be done in a lockless way and user space is notified about staged
+ * measurements being carried over to the secondary kernel, so that it does not
+ * save them twice.
+ *
+ * Return: Zero on success, a negative value otherwise.
+ */
+int ima_queue_staged_delete_all(void)
+{
+ LIST_HEAD(ima_measurements_trim);
+
+ mutex_lock(&ima_extend_list_mutex);
+ if (list_empty(&ima_measurements_staged)) {
+ mutex_unlock(&ima_extend_list_mutex);
+ return -ENOENT;
+ }
+
+ if (ima_measurements_suspended) {
+ mutex_unlock(&ima_extend_list_mutex);
+ return -ESTALE;
+ }
+
+ list_replace(&ima_measurements_staged, &ima_measurements_trim);
+ INIT_LIST_HEAD(&ima_measurements_staged);
+
+ atomic_long_set(&ima_num_records[BINARY_STAGED], 0);
+
+ if (IS_ENABLED(CONFIG_IMA_KEXEC))
+ binary_runtime_size[BINARY_STAGED] = 0;
+
+ mutex_unlock(&ima_extend_list_mutex);
+
+ ima_queue_delete(&ima_measurements_trim);
+ return 0;
+}
+
+/**
+ * ima_queue_delete - Delete measurements
+ * @head: List head measurements are deleted from
+ *
+ * Delete the measurements from the passed list head completely if the
+ * hash table is not enabled, or partially (only the template data), if the
+ * hash table is used.
+ */
+static void ima_queue_delete(struct list_head *head)
+{
+ struct ima_queue_entry *qe, *qe_tmp;
+ unsigned int i;
+
+ list_for_each_entry_safe(qe, qe_tmp, head, later) {
+ /*
+ * Safe to free template_data here without synchronize_rcu()
+ * because the only htable reader, ima_lookup_digest_entry(),
+ * accesses only entry->digests, not template_data. If new
+ * htable readers are added that access template_data, a
+ * synchronize_rcu() is required here.
+ */
+ for (i = 0; i < qe->entry->template_desc->num_fields; i++) {
+ kfree(qe->entry->template_data[i].data);
+ qe->entry->template_data[i].data = NULL;
+ qe->entry->template_data[i].len = 0;
+ }
+
+ list_del(&qe->later);
+
+ /* No leak if condition is false, referenced by ima_htable. */
+ if (IS_ENABLED(CONFIG_IMA_DISABLE_HTABLE)) {
+ kfree(qe->entry->digests);
+ kfree(qe->entry);
+ kfree(qe);
+ }
+ }
+}
+
int ima_restore_measurement_entry(struct ima_template_entry *entry)
{
int result = 0;
--
2.43.0
^ permalink raw reply related
* [PATCH v7 08/12] ima: Introduce ima_dump_measurement()
From: Roberto Sassu @ 2026-06-05 17:22 UTC (permalink / raw)
To: corbet, skhan, zohar, dmitry.kasatkin, eric.snowberg, paul,
jmorris, serge
Cc: linux-doc, linux-kernel, linux-integrity, linux-security-module,
gregorylumen, chenste, nramas, Roberto Sassu
In-Reply-To: <20260605172236.2042045-1-roberto.sassu@huaweicloud.com>
From: Roberto Sassu <roberto.sassu@huawei.com>
Introduce ima_dump_measurement() to simplify the code of
ima_dump_measurement_list() and to avoid repeating the
ima_dump_measurement() code block if iteration occurs on multiple lists.
No functional change: only code moved to a separate function.
Link: https://github.com/linux-integrity/linux/issues/1
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
---
security/integrity/ima/ima_kexec.c | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)
diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index 8dc9459622b3..26d41974429e 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -80,6 +80,17 @@ static int ima_alloc_kexec_file_buf(size_t segment_size)
return 0;
}
+static int ima_dump_measurement(struct ima_kexec_hdr *khdr,
+ struct ima_queue_entry *qe)
+{
+ if (ima_kexec_file.count >= ima_kexec_file.size)
+ return -EINVAL;
+
+ khdr->count++;
+ ima_measurements_show(&ima_kexec_file, qe);
+ return 0;
+}
+
static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
unsigned long segment_size)
{
@@ -97,13 +108,9 @@ static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
khdr.version = 1;
/* This is an append-only list, no need to hold the RCU read lock */
list_for_each_entry_rcu(qe, &ima_measurements, later, true) {
- if (ima_kexec_file.count < ima_kexec_file.size) {
- khdr.count++;
- ima_measurements_show(&ima_kexec_file, qe);
- } else {
- ret = -EINVAL;
+ ret = ima_dump_measurement(&khdr, qe);
+ if (ret < 0)
break;
- }
}
/*
--
2.43.0
^ permalink raw reply related
* [PATCH v7 07/12] ima: Use snprintf() in create_securityfs_measurement_lists
From: Roberto Sassu @ 2026-06-05 17:22 UTC (permalink / raw)
To: corbet, skhan, zohar, dmitry.kasatkin, eric.snowberg, paul,
jmorris, serge
Cc: linux-doc, linux-kernel, linux-integrity, linux-security-module,
gregorylumen, chenste, nramas, Roberto Sassu
In-Reply-To: <20260605172236.2042045-1-roberto.sassu@huaweicloud.com>
From: Roberto Sassu <roberto.sassu@huawei.com>
Use the more secure snprintf() function (accepting the buffer size) in
create_securityfs_measurement_lists().
No functional change: sprintf() and snprintf() have the same behavior.
Link: https://github.com/linux-integrity/linux/issues/1
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
---
security/integrity/ima/ima_fs.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index 91bd831d070f..f6ecee2d7699 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -503,11 +503,13 @@ static int __init create_securityfs_measurement_lists(void)
struct dentry *dentry;
if (algo == HASH_ALGO__LAST)
- sprintf(file_name, "ascii_runtime_measurements_tpm_alg_%x",
- ima_tpm_chip->allocated_banks[i].alg_id);
+ snprintf(file_name, sizeof(file_name),
+ "ascii_runtime_measurements_tpm_alg_%x",
+ ima_tpm_chip->allocated_banks[i].alg_id);
else
- sprintf(file_name, "ascii_runtime_measurements_%s",
- hash_algo_name[algo]);
+ snprintf(file_name, sizeof(file_name),
+ "ascii_runtime_measurements_%s",
+ hash_algo_name[algo]);
dentry = securityfs_create_file(file_name, S_IRUSR | S_IRGRP,
ima_dir, (void *)(uintptr_t)i,
&ima_ascii_measurements_ops);
@@ -515,11 +517,13 @@ static int __init create_securityfs_measurement_lists(void)
return PTR_ERR(dentry);
if (algo == HASH_ALGO__LAST)
- sprintf(file_name, "binary_runtime_measurements_tpm_alg_%x",
- ima_tpm_chip->allocated_banks[i].alg_id);
+ snprintf(file_name, sizeof(file_name),
+ "binary_runtime_measurements_tpm_alg_%x",
+ ima_tpm_chip->allocated_banks[i].alg_id);
else
- sprintf(file_name, "binary_runtime_measurements_%s",
- hash_algo_name[algo]);
+ snprintf(file_name, sizeof(file_name),
+ "binary_runtime_measurements_%s",
+ hash_algo_name[algo]);
dentry = securityfs_create_file(file_name, S_IRUSR | S_IRGRP,
ima_dir, (void *)(uintptr_t)i,
&ima_measurements_ops);
--
2.43.0
^ permalink raw reply related
* [PATCH v7 06/12] ima: Mediate open/release method of the measurements list
From: Roberto Sassu @ 2026-06-05 17:22 UTC (permalink / raw)
To: corbet, skhan, zohar, dmitry.kasatkin, eric.snowberg, paul,
jmorris, serge
Cc: linux-doc, linux-kernel, linux-integrity, linux-security-module,
gregorylumen, chenste, nramas, Roberto Sassu
In-Reply-To: <20260605172236.2042045-1-roberto.sassu@huaweicloud.com>
From: Roberto Sassu <roberto.sassu@huawei.com>
Introduce the ima_measure_users counter, to implement a semaphore-like
locking scheme where the binary and ASCII measurements list interfaces can
be concurrently opened by multiple readers, or alternatively by a single
writer. In addition, allow the same writer to open the other interfaces for
write or read/write, so that it can see the same measurement state across
all the interfaces.
A semaphore cannot be used because the kernel cannot return to user space
with a lock held.
Introduce the ima_measure_lock() and ima_measure_unlock() primitives, to
respectively lock/unlock the interfaces (safely with the ima_measure_users
counter, without holding a lock).
Finally, introduce _ima_measurements_open() to lock the interface before
seq_open(), and call it from ima_measurements_open() and
ima_ascii_measurements_open(). And, introduce ima_measurements_release(),
to unlock the interface.
Require CAP_SYS_ADMIN if the interface is opened for write (not possible
for the current measurements interfaces, since they only have read
permission).
No functional changes: multiple readers are allowed as before.
Link: https://github.com/linux-integrity/linux/issues/1
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
security/integrity/ima/ima_fs.c | 102 ++++++++++++++++++++++++++++++--
1 file changed, 98 insertions(+), 4 deletions(-)
diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index dcdc4cb8fa0f..91bd831d070f 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -25,6 +25,10 @@
#include "ima.h"
static DEFINE_MUTEX(ima_write_mutex);
+static DEFINE_MUTEX(ima_measure_mutex);
+static long ima_measure_users;
+static struct task_struct *measure_writer;
+static long measure_writer_extra_writes;
bool ima_canonical_fmt;
static int __init default_canonical_fmt_setup(char *str)
@@ -209,16 +213,105 @@ static const struct seq_operations ima_measurments_seqops = {
.show = ima_measurements_show
};
+static int ima_measure_lock(bool write)
+{
+ mutex_lock(&ima_measure_mutex);
+ /* Overflow check. */
+ if (!write && ima_measure_users == LONG_MAX) {
+ mutex_unlock(&ima_measure_mutex);
+ return -ENFILE;
+ }
+
+ /* Same writer can do additional writes or read/writes. */
+ if (write && current == measure_writer) {
+ measure_writer_extra_writes++;
+ mutex_unlock(&ima_measure_mutex);
+ return 0;
+ }
+
+ /*
+ * ima_measure_users: > 0 open readers
+ * ima_measure_users: == -1 open writer
+ */
+ if ((write && ima_measure_users != 0) ||
+ (!write && ima_measure_users < 0)) {
+ mutex_unlock(&ima_measure_mutex);
+ return -EBUSY;
+ }
+
+ if (write) {
+ ima_measure_users--;
+ /* Pointer valid, no reuse while the file descriptor is open. */
+ measure_writer = current;
+ } else {
+ ima_measure_users++;
+ }
+ mutex_unlock(&ima_measure_mutex);
+ return 0;
+}
+
+static void ima_measure_unlock(bool write)
+{
+ mutex_lock(&ima_measure_mutex);
+ /* Decrement additional writes or read/writes. */
+ if (write && current == measure_writer &&
+ measure_writer_extra_writes != 0) {
+ measure_writer_extra_writes--;
+ mutex_unlock(&ima_measure_mutex);
+ return;
+ }
+ if (write) {
+ ima_measure_users++;
+ measure_writer = NULL;
+ } else {
+ ima_measure_users--;
+ }
+ mutex_unlock(&ima_measure_mutex);
+}
+
+static int _ima_measurements_open(struct inode *inode, struct file *file,
+ const struct seq_operations *seq_ops)
+{
+ bool write = (file->f_mode & FMODE_WRITE);
+ int ret;
+
+ if (write && !capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ ret = ima_measure_lock(write);
+ if (ret < 0)
+ return ret;
+
+ ret = seq_open(file, seq_ops);
+ if (ret < 0)
+ ima_measure_unlock(write);
+
+ return ret;
+}
+
static int ima_measurements_open(struct inode *inode, struct file *file)
{
- return seq_open(file, &ima_measurments_seqops);
+ return _ima_measurements_open(inode, file, &ima_measurments_seqops);
+}
+
+static int ima_measurements_release(struct inode *inode, struct file *file)
+{
+ bool write = (file->f_mode & FMODE_WRITE);
+ int ret;
+
+ /* seq_release() always returns zero. */
+ ret = seq_release(inode, file);
+
+ ima_measure_unlock(write);
+
+ return ret;
}
static const struct file_operations ima_measurements_ops = {
.open = ima_measurements_open,
.read = seq_read,
.llseek = seq_lseek,
- .release = seq_release,
+ .release = ima_measurements_release,
};
void ima_print_digest(struct seq_file *m, u8 *digest, u32 size)
@@ -283,14 +376,15 @@ static const struct seq_operations ima_ascii_measurements_seqops = {
static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
{
- return seq_open(file, &ima_ascii_measurements_seqops);
+ return _ima_measurements_open(inode, file,
+ &ima_ascii_measurements_seqops);
}
static const struct file_operations ima_ascii_measurements_ops = {
.open = ima_ascii_measurements_open,
.read = seq_read,
.llseek = seq_lseek,
- .release = seq_release,
+ .release = ima_measurements_release,
};
static ssize_t ima_read_policy(char *path)
--
2.43.0
^ permalink raw reply related
* [PATCH v7 05/12] ima: Introduce _ima_measurements_start() and _ima_measurements_next()
From: Roberto Sassu @ 2026-06-05 17:22 UTC (permalink / raw)
To: corbet, skhan, zohar, dmitry.kasatkin, eric.snowberg, paul,
jmorris, serge
Cc: linux-doc, linux-kernel, linux-integrity, linux-security-module,
gregorylumen, chenste, nramas, Roberto Sassu
In-Reply-To: <20260605172236.2042045-1-roberto.sassu@huaweicloud.com>
From: Roberto Sassu <roberto.sassu@huawei.com>
Introduce _ima_measurements_start() and _ima_measurements_next(), renamed
from ima_measurements_start() and ima_measurements_next(), to include the
list head as an additional parameter, so that iteration on different lists
can be implemented by calling those functions.
No functional change: ima_measurements_start() and ima_measurements_next()
pass the ima_measurements list head, used before. They become wrappers for
the new functions.
Link: https://github.com/linux-integrity/linux/issues/1
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
---
security/integrity/ima/ima_fs.c | 20 ++++++++++++++++----
1 file changed, 16 insertions(+), 4 deletions(-)
diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index fcfcf7b6eae2..dcdc4cb8fa0f 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -72,14 +72,15 @@ static const struct file_operations ima_measurements_count_ops = {
};
/* returns pointer to hlist_node */
-static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
+static void *_ima_measurements_start(struct seq_file *m, loff_t *pos,
+ struct list_head *head)
{
loff_t l = *pos;
struct ima_queue_entry *qe;
/* we need a lock since pos could point beyond last element */
rcu_read_lock();
- list_for_each_entry_rcu(qe, &ima_measurements, later) {
+ list_for_each_entry_rcu(qe, head, later) {
if (!l--) {
rcu_read_unlock();
return qe;
@@ -89,7 +90,13 @@ static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
return NULL;
}
-static void *ima_measurements_next(struct seq_file *m, void *v, loff_t *pos)
+static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
+{
+ return _ima_measurements_start(m, pos, &ima_measurements);
+}
+
+static void *_ima_measurements_next(struct seq_file *m, void *v, loff_t *pos,
+ struct list_head *head)
{
struct ima_queue_entry *qe = v;
@@ -101,7 +108,12 @@ static void *ima_measurements_next(struct seq_file *m, void *v, loff_t *pos)
rcu_read_unlock();
(*pos)++;
- return (&qe->later == &ima_measurements) ? NULL : qe;
+ return (&qe->later == head) ? NULL : qe;
+}
+
+static void *ima_measurements_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ return _ima_measurements_next(m, v, pos, &ima_measurements);
}
static void ima_measurements_stop(struct seq_file *m, void *v)
--
2.43.0
^ permalink raw reply related
* [PATCH v7 04/12] ima: Introduce per binary measurements list type binary_runtime_size value
From: Roberto Sassu @ 2026-06-05 17:22 UTC (permalink / raw)
To: corbet, skhan, zohar, dmitry.kasatkin, eric.snowberg, paul,
jmorris, serge
Cc: linux-doc, linux-kernel, linux-integrity, linux-security-module,
gregorylumen, chenste, nramas, Roberto Sassu
In-Reply-To: <20260605172236.2042045-1-roberto.sassu@huaweicloud.com>
From: Roberto Sassu <roberto.sassu@huawei.com>
Make binary_runtime_size as an array, to have separate counters per binary
measurements list type. Currently, define the BINARY type for the existing
binary measurements list.
Introduce ima_update_binary_runtime_size() to facilitate updating a
binary_runtime_size value with a given binary measurement list type.
Also add the binary measurements list type parameter to
ima_get_binary_runtime_size(), to retrieve the desired value. Retrieving
the value is now done under the ima_extend_list_mutex, since there can be
concurrent updates.
No functional change (except for the mutex usage, that fixes the
concurrency issue): the BINARY array element is equivalent to the old
binary_runtime_size.
Link: https://github.com/linux-integrity/linux/issues/1
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
security/integrity/ima/ima.h | 2 +-
security/integrity/ima/ima_kexec.c | 5 ++--
security/integrity/ima/ima_queue.c | 40 +++++++++++++++++++++---------
3 files changed, 32 insertions(+), 15 deletions(-)
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 8f457f2c7b79..c00c133a140f 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -319,7 +319,7 @@ int ima_restore_measurement_entry(struct ima_template_entry *entry);
int ima_restore_measurement_list(loff_t bufsize, void *buf);
int ima_measurements_show(struct seq_file *m, void *v);
int __init ima_init_htable(void);
-unsigned long ima_get_binary_runtime_size(void);
+unsigned long ima_get_binary_runtime_size(enum binary_lists binary_list);
int ima_init_template(void);
void ima_init_template_list(void);
int __init ima_init_digests(void);
diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index 1a0211a12ea4..8dc9459622b3 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -42,7 +42,7 @@ void ima_measure_kexec_event(const char *event_name)
long len;
int n;
- buf_size = ima_get_binary_runtime_size();
+ buf_size = ima_get_binary_runtime_size(BINARY);
len = atomic_long_read(&ima_num_records[BINARY]);
n = scnprintf(ima_kexec_event, IMA_KEXEC_EVENT_LEN,
@@ -159,7 +159,8 @@ void ima_add_kexec_buffer(struct kimage *image)
else
extra_memory = CONFIG_IMA_KEXEC_EXTRA_MEMORY_KB * 1024;
- binary_runtime_size = ima_get_binary_runtime_size() + extra_memory;
+ binary_runtime_size = ima_get_binary_runtime_size(BINARY) +
+ extra_memory;
if (binary_runtime_size >= ULONG_MAX - PAGE_SIZE)
kexec_segment_size = ULONG_MAX;
diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
index 012e725ed4fc..618694d5c082 100644
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -27,9 +27,11 @@ static struct tpm_digest *digests;
LIST_HEAD(ima_measurements); /* list of all measurements */
#ifdef CONFIG_IMA_KEXEC
-static unsigned long binary_runtime_size;
+static unsigned long binary_runtime_size[BINARY__LAST];
#else
-static unsigned long binary_runtime_size = ULONG_MAX;
+static unsigned long binary_runtime_size[BINARY__LAST] = {
+ [0 ... BINARY__LAST - 1] = ULONG_MAX
+};
#endif
atomic_long_t ima_num_records[BINARY__LAST] = {
@@ -128,6 +130,20 @@ static int get_binary_runtime_size(struct ima_template_entry *entry)
return size;
}
+static void ima_update_binary_runtime_size(struct ima_template_entry *entry,
+ enum binary_lists binary_list)
+{
+ int size;
+
+ if (binary_runtime_size[binary_list] == ULONG_MAX)
+ return;
+
+ size = get_binary_runtime_size(entry);
+ binary_runtime_size[binary_list] =
+ (binary_runtime_size[binary_list] < ULONG_MAX - size) ?
+ binary_runtime_size[binary_list] + size : ULONG_MAX;
+}
+
/* ima_add_template_entry helper function:
* - Add template entry to the measurement list and hash table, for
* all entries except those carried across kexec.
@@ -160,13 +176,7 @@ static int ima_add_digest_entry(struct ima_template_entry *entry,
hlist_add_head_rcu(&qe->hnext, &htable[key]);
}
- if (binary_runtime_size != ULONG_MAX) {
- int size;
-
- size = get_binary_runtime_size(entry);
- binary_runtime_size = (binary_runtime_size < ULONG_MAX - size) ?
- binary_runtime_size + size : ULONG_MAX;
- }
+ ima_update_binary_runtime_size(entry, BINARY);
return 0;
}
@@ -175,12 +185,18 @@ static int ima_add_digest_entry(struct ima_template_entry *entry,
* entire binary_runtime_measurement list, including the ima_kexec_hdr
* structure.
*/
-unsigned long ima_get_binary_runtime_size(void)
+unsigned long ima_get_binary_runtime_size(enum binary_lists binary_list)
{
- if (binary_runtime_size >= (ULONG_MAX - sizeof(struct ima_kexec_hdr)))
+ unsigned long val;
+
+ mutex_lock(&ima_extend_list_mutex);
+ val = binary_runtime_size[binary_list];
+ mutex_unlock(&ima_extend_list_mutex);
+
+ if (val >= (ULONG_MAX - sizeof(struct ima_kexec_hdr)))
return ULONG_MAX;
else
- return binary_runtime_size + sizeof(struct ima_kexec_hdr);
+ return val + sizeof(struct ima_kexec_hdr);
}
static int ima_pcr_extend(struct tpm_digest *digests_arg, int pcr)
--
2.43.0
^ permalink raw reply related
* [PATCH v7 03/12] ima: Introduce per binary measurements list type ima_num_records counter
From: Roberto Sassu @ 2026-06-05 17:22 UTC (permalink / raw)
To: corbet, skhan, zohar, dmitry.kasatkin, eric.snowberg, paul,
jmorris, serge
Cc: linux-doc, linux-kernel, linux-integrity, linux-security-module,
gregorylumen, chenste, nramas, Roberto Sassu
In-Reply-To: <20260605172236.2042045-1-roberto.sassu@huaweicloud.com>
From: Roberto Sassu <roberto.sassu@huawei.com>
Make ima_num_records as an array, to have separate counters per binary
measurements list type. Currently, define the BINARY type for the existing
binary measurements list.
No functional change: the BINARY type is equivalent to the value without
the array.
Link: https://github.com/linux-integrity/linux/issues/1
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
---
security/integrity/ima/ima.h | 9 ++++++++-
security/integrity/ima/ima_fs.c | 2 +-
security/integrity/ima/ima_kexec.c | 2 +-
security/integrity/ima/ima_queue.c | 6 ++++--
4 files changed, 14 insertions(+), 5 deletions(-)
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 0e41c2113efd..8f457f2c7b79 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -28,6 +28,13 @@ enum ima_show_type { IMA_SHOW_BINARY, IMA_SHOW_BINARY_NO_FIELD_LEN,
IMA_SHOW_BINARY_OLD_STRING_FMT, IMA_SHOW_ASCII };
enum tpm_pcrs { TPM_PCR0 = 0, TPM_PCR8 = 8, TPM_PCR10 = 10 };
+/*
+ * BINARY: current binary measurements list
+ */
+enum binary_lists {
+ BINARY, BINARY__LAST
+};
+
/* digest size for IMA, fits SHA1 or MD5 */
#define IMA_DIGEST_SIZE SHA1_DIGEST_SIZE
#define IMA_EVENT_NAME_LEN_MAX 255
@@ -326,7 +333,7 @@ int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
extern spinlock_t ima_queue_lock;
/* Total number of measurement list records since hard boot. */
-extern atomic_long_t ima_num_records;
+extern atomic_long_t ima_num_records[BINARY__LAST];
/* Total number of violations since hard boot. */
extern atomic_long_t ima_num_violations;
extern struct hlist_head __rcu *ima_htable;
diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index 523d3e81f631..fcfcf7b6eae2 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -63,7 +63,7 @@ static ssize_t ima_show_measurements_count(struct file *filp,
char __user *buf,
size_t count, loff_t *ppos)
{
- return ima_show_counter(buf, count, ppos, &ima_num_records);
+ return ima_show_counter(buf, count, ppos, &ima_num_records[BINARY]);
}
static const struct file_operations ima_measurements_count_ops = {
diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index 77ad370dbc37..1a0211a12ea4 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -43,7 +43,7 @@ void ima_measure_kexec_event(const char *event_name)
int n;
buf_size = ima_get_binary_runtime_size();
- len = atomic_long_read(&ima_num_records);
+ len = atomic_long_read(&ima_num_records[BINARY]);
n = scnprintf(ima_kexec_event, IMA_KEXEC_EVENT_LEN,
"kexec_segment_size=%lu;ima_binary_runtime_size=%lu;"
diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
index a31b75d9302b..012e725ed4fc 100644
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -32,7 +32,9 @@ static unsigned long binary_runtime_size;
static unsigned long binary_runtime_size = ULONG_MAX;
#endif
-atomic_long_t ima_num_records = ATOMIC_LONG_INIT(0);
+atomic_long_t ima_num_records[BINARY__LAST] = {
+ [0 ... BINARY__LAST - 1] = ATOMIC_LONG_INIT(0)
+};
atomic_long_t ima_num_violations = ATOMIC_LONG_INIT(0);
/* key: inode (before secure-hashing a file) */
@@ -152,7 +154,7 @@ static int ima_add_digest_entry(struct ima_template_entry *entry,
htable = rcu_dereference_protected(ima_htable,
lockdep_is_held(&ima_extend_list_mutex));
- atomic_long_inc(&ima_num_records);
+ atomic_long_inc(&ima_num_records[BINARY]);
if (update_htable) {
key = ima_hash_key(entry->digests[ima_hash_algo_idx].digest);
hlist_add_head_rcu(&qe->hnext, &htable[key]);
--
2.43.0
^ permalink raw reply related
* [PATCH v7 02/12] ima: Replace static htable queue with dynamically allocated array
From: Roberto Sassu @ 2026-06-05 17:22 UTC (permalink / raw)
To: corbet, skhan, zohar, dmitry.kasatkin, eric.snowberg, paul,
jmorris, serge
Cc: linux-doc, linux-kernel, linux-integrity, linux-security-module,
gregorylumen, chenste, nramas, Roberto Sassu
In-Reply-To: <20260605172236.2042045-1-roberto.sassu@huaweicloud.com>
From: Roberto Sassu <roberto.sassu@huawei.com>
The IMA hash table is a fixed-size array of hlist_head buckets:
struct hlist_head ima_htable[IMA_MEASURE_HTABLE_SIZE];
IMA_MEASURE_HTABLE_SIZE is (1 << IMA_HASH_BITS) = 1024 buckets, each a
struct hlist_head (one pointer, 8 bytes on 64-bit). That is 8 KiB allocated
in BSS for every kernel, regardless of whether IMA is ever used, and
regardless of how many measurements are actually made.
Replace the fixed-size array with a RCU-protected pointer to a dynamically
allocated array that is initialized in ima_init_htable(), which is called
from ima_init() during early boot. ima_init_htable() calls the static
function ima_alloc_replace_htable() which, other than initializing the hash
table the first time, can also hot-swap the existing hash table with a
blank one.
The allocation in ima_alloc_replace_htable() uses kcalloc() so the buckets
are zero-initialised (equivalent to HLIST_HEAD_INIT { .first = NULL }).
Callers of ima_alloc_replace_htable() must call synchronize_rcu() and free
the returned hash table.
Finally, access the hash table with rcu_dereference() in
ima_lookup_digest_entry() (reader side) and with
rcu_dereference_protected() in ima_add_digest_entry() (writer side).
No functional change: bucket count, hash function, and all locking remain
identical.
Link: https://github.com/linux-integrity/linux/issues/1
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
---
security/integrity/ima/ima.h | 3 +-
security/integrity/ima/ima_init.c | 5 ++++
security/integrity/ima/ima_queue.c | 48 ++++++++++++++++++++++++++----
3 files changed, 50 insertions(+), 6 deletions(-)
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index b3ad7eac6a1e..0e41c2113efd 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -311,6 +311,7 @@ bool ima_template_has_modsig(const struct ima_template_desc *ima_template);
int ima_restore_measurement_entry(struct ima_template_entry *entry);
int ima_restore_measurement_list(loff_t bufsize, void *buf);
int ima_measurements_show(struct seq_file *m, void *v);
+int __init ima_init_htable(void);
unsigned long ima_get_binary_runtime_size(void);
int ima_init_template(void);
void ima_init_template_list(void);
@@ -328,7 +329,7 @@ extern spinlock_t ima_queue_lock;
extern atomic_long_t ima_num_records;
/* Total number of violations since hard boot. */
extern atomic_long_t ima_num_violations;
-extern struct hlist_head ima_htable[IMA_MEASURE_HTABLE_SIZE];
+extern struct hlist_head __rcu *ima_htable;
static inline unsigned int ima_hash_key(u8 *digest)
{
diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
index a2f34f2d8ad7..7e0aa09a12e6 100644
--- a/security/integrity/ima/ima_init.c
+++ b/security/integrity/ima/ima_init.c
@@ -140,6 +140,11 @@ int __init ima_init(void)
rc = ima_init_digests();
if (rc != 0)
return rc;
+
+ rc = ima_init_htable();
+ if (rc != 0)
+ return rc;
+
rc = ima_add_boot_aggregate(); /* boot aggregate must be first entry */
if (rc != 0)
return rc;
diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
index 6bdaefc790c3..a31b75d9302b 100644
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -36,9 +36,7 @@ atomic_long_t ima_num_records = ATOMIC_LONG_INIT(0);
atomic_long_t ima_num_violations = ATOMIC_LONG_INIT(0);
/* key: inode (before secure-hashing a file) */
-struct hlist_head ima_htable[IMA_MEASURE_HTABLE_SIZE] = {
- [0 ... IMA_MEASURE_HTABLE_SIZE - 1] = HLIST_HEAD_INIT
-};
+struct hlist_head __rcu *ima_htable;
/* mutex protects atomicity of extending measurement list
* and extending the TPM PCR aggregate. Since tpm_extend can take
@@ -52,17 +50,53 @@ static DEFINE_MUTEX(ima_extend_list_mutex);
*/
static bool ima_measurements_suspended;
+/* Callers must call synchronize_rcu() and free the hash table. */
+static struct hlist_head *ima_alloc_replace_htable(void)
+{
+ struct hlist_head *old_htable, *new_htable;
+
+ /* Initializing to zeros is equivalent to call HLIST_HEAD_INIT. */
+ new_htable = kcalloc(IMA_MEASURE_HTABLE_SIZE, sizeof(struct hlist_head),
+ GFP_KERNEL);
+ if (!new_htable)
+ return ERR_PTR(-ENOMEM);
+
+ old_htable = rcu_replace_pointer(ima_htable, new_htable,
+ lockdep_is_held(&ima_extend_list_mutex));
+
+ return old_htable;
+}
+
+int __init ima_init_htable(void)
+{
+ struct hlist_head *old_htable;
+
+ mutex_lock(&ima_extend_list_mutex);
+ old_htable = ima_alloc_replace_htable();
+ mutex_unlock(&ima_extend_list_mutex);
+
+ if (IS_ERR(old_htable))
+ return PTR_ERR(old_htable);
+
+ /* Synchronize_rcu() and kfree() not necessary, only for robustness. */
+ synchronize_rcu();
+ kfree(old_htable);
+ return 0;
+}
+
/* lookup up the digest value in the hash table, and return the entry */
static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value,
int pcr)
{
struct ima_queue_entry *qe, *ret = NULL;
+ struct hlist_head *htable;
unsigned int key;
int rc;
key = ima_hash_key(digest_value);
rcu_read_lock();
- hlist_for_each_entry_rcu(qe, &ima_htable[key], hnext) {
+ htable = rcu_dereference(ima_htable);
+ hlist_for_each_entry_rcu(qe, &htable[key], hnext) {
rc = memcmp(qe->entry->digests[ima_hash_algo_idx].digest,
digest_value, hash_digest_size[ima_hash_algo]);
if ((rc == 0) && (qe->entry->pcr == pcr)) {
@@ -102,6 +136,7 @@ static int ima_add_digest_entry(struct ima_template_entry *entry,
bool update_htable)
{
struct ima_queue_entry *qe;
+ struct hlist_head *htable;
unsigned int key;
qe = kmalloc_obj(*qe);
@@ -114,10 +149,13 @@ static int ima_add_digest_entry(struct ima_template_entry *entry,
INIT_LIST_HEAD(&qe->later);
list_add_tail_rcu(&qe->later, &ima_measurements);
+ htable = rcu_dereference_protected(ima_htable,
+ lockdep_is_held(&ima_extend_list_mutex));
+
atomic_long_inc(&ima_num_records);
if (update_htable) {
key = ima_hash_key(entry->digests[ima_hash_algo_idx].digest);
- hlist_add_head_rcu(&qe->hnext, &ima_htable[key]);
+ hlist_add_head_rcu(&qe->hnext, &htable[key]);
}
if (binary_runtime_size != ULONG_MAX) {
--
2.43.0
^ permalink raw reply related
* [PATCH v7 01/12] ima: Remove ima_h_table structure
From: Roberto Sassu @ 2026-06-05 17:22 UTC (permalink / raw)
To: corbet, skhan, zohar, dmitry.kasatkin, eric.snowberg, paul,
jmorris, serge
Cc: linux-doc, linux-kernel, linux-integrity, linux-security-module,
gregorylumen, chenste, nramas, Roberto Sassu
In-Reply-To: <20260605172236.2042045-1-roberto.sassu@huaweicloud.com>
From: Roberto Sassu <roberto.sassu@huawei.com>
The ima_h_table structure is a collection of IMA measurement list
metadata - number of records in the IMA measurement list, number of
integrity violations, and a hash table containing the IMA template data
hash, needed to prevent measurement list record duplication.
Removing records from the measurement list needs to be reflected in the
hash table. As a pre-req to removing records from the measurement list,
separate those counters from the hash table, remove the ima_h_table
structure, and just replace the hash table pointer.
Finally, rename ima_show_htable_value(), ima_show_htable_violations()
and ima_htable_violations_ops respectively to ima_show_counter(),
ima_show_num_violations() and ima_num_violations_ops.
Link: https://github.com/linux-integrity/linux/issues/1
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
security/integrity/ima/ima.h | 11 +++++------
security/integrity/ima/ima_api.c | 2 +-
security/integrity/ima/ima_fs.c | 20 +++++++++-----------
security/integrity/ima/ima_kexec.c | 2 +-
security/integrity/ima/ima_queue.c | 15 ++++++++-------
5 files changed, 24 insertions(+), 26 deletions(-)
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 69e9bf0b82c6..b3ad7eac6a1e 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -324,12 +324,11 @@ int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
*/
extern spinlock_t ima_queue_lock;
-struct ima_h_table {
- atomic_long_t len; /* number of stored measurements in the list */
- atomic_long_t violations;
- struct hlist_head queue[IMA_MEASURE_HTABLE_SIZE];
-};
-extern struct ima_h_table ima_htable;
+/* Total number of measurement list records since hard boot. */
+extern atomic_long_t ima_num_records;
+/* Total number of violations since hard boot. */
+extern atomic_long_t ima_num_violations;
+extern struct hlist_head ima_htable[IMA_MEASURE_HTABLE_SIZE];
static inline unsigned int ima_hash_key(u8 *digest)
{
diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index 0916f24f005f..122d127e108d 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -146,7 +146,7 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
int result;
/* can overflow, only indicator */
- atomic_long_inc(&ima_htable.violations);
+ atomic_long_inc(&ima_num_violations);
result = ima_alloc_init_template(&event_data, &entry, NULL);
if (result < 0) {
diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index ca4931a95098..523d3e81f631 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -38,8 +38,8 @@ __setup("ima_canonical_fmt", default_canonical_fmt_setup);
static int valid_policy = 1;
-static ssize_t ima_show_htable_value(char __user *buf, size_t count,
- loff_t *ppos, atomic_long_t *val)
+static ssize_t ima_show_counter(char __user *buf, size_t count, loff_t *ppos,
+ atomic_long_t *val)
{
char tmpbuf[32]; /* greater than largest 'long' string value */
ssize_t len;
@@ -48,15 +48,14 @@ static ssize_t ima_show_htable_value(char __user *buf, size_t count,
return simple_read_from_buffer(buf, count, ppos, tmpbuf, len);
}
-static ssize_t ima_show_htable_violations(struct file *filp,
- char __user *buf,
- size_t count, loff_t *ppos)
+static ssize_t ima_show_num_violations(struct file *filp, char __user *buf,
+ size_t count, loff_t *ppos)
{
- return ima_show_htable_value(buf, count, ppos, &ima_htable.violations);
+ return ima_show_counter(buf, count, ppos, &ima_num_violations);
}
-static const struct file_operations ima_htable_violations_ops = {
- .read = ima_show_htable_violations,
+static const struct file_operations ima_num_violations_ops = {
+ .read = ima_show_num_violations,
.llseek = generic_file_llseek,
};
@@ -64,8 +63,7 @@ static ssize_t ima_show_measurements_count(struct file *filp,
char __user *buf,
size_t count, loff_t *ppos)
{
- return ima_show_htable_value(buf, count, ppos, &ima_htable.len);
-
+ return ima_show_counter(buf, count, ppos, &ima_num_records);
}
static const struct file_operations ima_measurements_count_ops = {
@@ -545,7 +543,7 @@ int __init ima_fs_init(void)
}
dentry = securityfs_create_file("violations", S_IRUSR | S_IRGRP,
- ima_dir, NULL, &ima_htable_violations_ops);
+ ima_dir, NULL, &ima_num_violations_ops);
if (IS_ERR(dentry)) {
ret = PTR_ERR(dentry);
goto out;
diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index 36a34c54de58..77ad370dbc37 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -43,7 +43,7 @@ void ima_measure_kexec_event(const char *event_name)
int n;
buf_size = ima_get_binary_runtime_size();
- len = atomic_long_read(&ima_htable.len);
+ len = atomic_long_read(&ima_num_records);
n = scnprintf(ima_kexec_event, IMA_KEXEC_EVENT_LEN,
"kexec_segment_size=%lu;ima_binary_runtime_size=%lu;"
diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
index 319522450854..6bdaefc790c3 100644
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -32,11 +32,12 @@ static unsigned long binary_runtime_size;
static unsigned long binary_runtime_size = ULONG_MAX;
#endif
+atomic_long_t ima_num_records = ATOMIC_LONG_INIT(0);
+atomic_long_t ima_num_violations = ATOMIC_LONG_INIT(0);
+
/* key: inode (before secure-hashing a file) */
-struct ima_h_table ima_htable = {
- .len = ATOMIC_LONG_INIT(0),
- .violations = ATOMIC_LONG_INIT(0),
- .queue[0 ... IMA_MEASURE_HTABLE_SIZE - 1] = HLIST_HEAD_INIT
+struct hlist_head ima_htable[IMA_MEASURE_HTABLE_SIZE] = {
+ [0 ... IMA_MEASURE_HTABLE_SIZE - 1] = HLIST_HEAD_INIT
};
/* mutex protects atomicity of extending measurement list
@@ -61,7 +62,7 @@ static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value,
key = ima_hash_key(digest_value);
rcu_read_lock();
- hlist_for_each_entry_rcu(qe, &ima_htable.queue[key], hnext) {
+ hlist_for_each_entry_rcu(qe, &ima_htable[key], hnext) {
rc = memcmp(qe->entry->digests[ima_hash_algo_idx].digest,
digest_value, hash_digest_size[ima_hash_algo]);
if ((rc == 0) && (qe->entry->pcr == pcr)) {
@@ -113,10 +114,10 @@ static int ima_add_digest_entry(struct ima_template_entry *entry,
INIT_LIST_HEAD(&qe->later);
list_add_tail_rcu(&qe->later, &ima_measurements);
- atomic_long_inc(&ima_htable.len);
+ atomic_long_inc(&ima_num_records);
if (update_htable) {
key = ima_hash_key(entry->digests[ima_hash_algo_idx].digest);
- hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
+ hlist_add_head_rcu(&qe->hnext, &ima_htable[key]);
}
if (binary_runtime_size != ULONG_MAX) {
--
2.43.0
^ permalink raw reply related
* [PATCH v7 00/12] ima: Exporting and deleting IMA measurement records from kernel memory
From: Roberto Sassu @ 2026-06-05 17:22 UTC (permalink / raw)
To: corbet, skhan, zohar, dmitry.kasatkin, eric.snowberg, paul,
jmorris, serge
Cc: linux-doc, linux-kernel, linux-integrity, linux-security-module,
gregorylumen, chenste, nramas, Roberto Sassu
From: Roberto Sassu <roberto.sassu@huawei.com>
Introduction
============
The IMA measurements list is currently stored in the kernel memory.
Memory occupation grows linearly with the number of records, and can
become a problem especially in environments with reduced resources.
While there is an advantage in keeping the IMA measurements list in
kernel memory, so that it is always available for reading from the
securityfs interfaces, storing it elsewhere would make it possible to
free precious memory for other kernel usage.
The IMA measurements list needs to be retained and safely stored for new
attestation servers to validate it. Assuming the IMA measurements list
is properly saved, storing it outside the kernel does not introduce
security issues, since its integrity is anyway protected by the TPM.
Hence, the new IMA staging mechanism is introduced to export IMA
measurements to user space and delete them from kernel space.
Staging consists in atomically moving the current measurements list to a
temporary list, so that measurements can be deleted afterwards. The
staging operation locks the hot path (racing with addition of new
measurements) for a very short time, only for swapping the list
pointers. Deletion of the measurements instead is done locklessly, away
from the hot path.
There are two flavors of the staging mechanism. In the staging with
prompt, all current measurements are staged, read and deleted upon
confirmation. In the staging and deleting flavor, N measurements are
staged from the beginning of the current measurements list and
immediately deleted without confirmation.
Usage
=====
The IMA staging mechanism can be enabled from the kernel configuration
with the CONFIG_IMA_STAGING option. This option prevents inadvertently
removing the IMA measurement list on systems which do not properly save
it.
If the option is enabled, IMA duplicates the current securityfs
measurements interfaces (both binary and ASCII), by adding the _staged
file suffix. Both the original and the staging interfaces gain the write
permission for the root user and group, but require the process to have
CAP_SYS_ADMIN set.
The staging mechanism supports two flavors.
Staging with prompt
~~~~~~~~~~~~~~~~~~~
The current measurement list is moved to a temporary staging area,
allowing it to be saved to external storage, before being deleted upon
confirmation.
This staging process is achieved with the following steps.
1. echo A > <_staged interface>: the user requests IMA to stage the
entire measurements list;
2. cat <_staged interface>: the user reads the staged measurements;
3. echo D > <_staged interface>: the user requests IMA to delete
staged measurements.
Staging and deleting
~~~~~~~~~~~~~~~~~~~~
N measurements are staged to a temporary staging area, and immediately
deleted without further confirmation.
This staging process is achieved with the following steps.
1. cat <original interface>: the user reads the current measurements
list and determines what the value N for staging should be;
2. echo N > <original interface>: the user requests IMA to delete N
measurements from the current measurements list.
Management of Staged Measurements
=================================
Since with the staging mechanism measurement records are removed from
the kernel, the staged measurements need to be saved in a storage and
concatenated together, so that they can be presented during remote
attestation as if staging was never done. This task can be accomplished
by a remote attestation agent modified to support staging, or a system
service.
Patch set content
=================
Patches 1-8 are preparatory patches to quickly replace the hash table,
maintain separate counters for the different measurements list types,
mediate access to the measurements list interface, and simplify the staging
patches.
Patch 9 introduces the staging with prompt flavor. Patch 10 makes it
possible to flush the hash table when deleting all the staged measurements.
Patch 11 introduces the staging and deleting flavor. Patch 12 adds the
documentation of the staging mechanism.
Changelog
=========
v6:
- Make ima_extend_list_mutex as static since it is not needed anymore by
ima_dump_measurement_list() (suggested by Mimi)
- Export ima_flush_htable in patch 11 instead of 10 (suggested by Mimi)
- Add clarification in the documentation regarding a proactive remote
attestation agent, and storing all the measurements in the storage
(suggested by Mimi)
v5:
- Add motivation for the ima_flush_htable= kernel option (suggested by
Mimi)
- New documentation title and fixes (suggested by Mimi)
- Allow stage all command on the _staged interface instead of the original
- Set CONFIG_IMA_STAGING default to n (suggested by Mimi)
- Rename ima_num_entries to ima_num_records (suggested by Mimi)
- Comment for ima_num_records and ima_num_violations (suggested by Mimi)
- Add overflow check in ima_measure_lock()
- Allow a writer to open for write or read/write the other staging
interfaces
- Ignore ppos in _ima_measurements_write()
- Implement lockless kexec measurement lists dump by denying
staging/delete after measurement suspend (collapse patch 12 into 9 and
11)
- Refuse delete based on measurement suspend instead of using
ima_copied_flags (suggested by Mimi)
- Add staging/deleting functions documentation
v4:
- Add write permission to the original measurement interface, and move
the A and N staging commands to that interface
- Explain better the two staging flavors and highlight that the staging
and delete only stages measurements internally
- Rename ima_queue_staged_delete_partial() to ima_queue_delete_partial()
- Replace ima_staged_measurements_prepended with per measurements list
flag to avoid copying staged and active list measurements twice
- Optimize the staging and deleting flavor by locklessly determining the
cut position in the active list, and immediately deleting entries
without explicit staging and splicing (suggested by Steven Chen)
v3:
- Add Kconfig option to enable the staging mechanism (suggested by Mimi)
- Change the meaning of BINARY_STAGED to be just the staged measurements
- Separate the two staging flavors in two different functions:
ima_queue_staged_delete_all() for staging with prompt,
ima_queue_staged_delete_partial() for staging and deleting
- Delete N entries without staging first (suggested by Mimi)
- Avoid duplicate staged entries if there is contention between the
measurements list interfaces and kexec
v2:
- New patch to move measurements and violation counters outside the
ima_h_table structure
- New patch to quickly replace the hash table
- Forbid partial deletion when flushing hash table (suggested by Mimi)
- Ignore ima_flush_htable if CONFIG_IMA_DISABLE_HTABLE is enabled
- BINARY_SIZE_* renamed to BINARY_* for better clarity
- Removed ima_measurements_staged_exist and testing list empty instead
- ima_queue_stage_trim() and ima_queue_delete_staged_trimmed() renamed to
ima_queue_stage() and ima_queue_delete_staged()
- New delete interval [1, ULONG_MAX - 1]
- Rename ima_measure_lock to ima_measure_mutex
- Move seq_open() and seq_release() outside the ima_measure_mutex lock
- Drop ima_measurements_staged_read() and use seq_read() instead
- Optimize create_securityfs_measurement_lists() changes
- New file name format with _staged suffix at the end of the file name
- Use _rcu list variant in ima_dump_measurement_list()
- Remove support for direct trimming and splice the remaining entries to
the active list (suggested by Mimi)
- Hot swap the hash table if flushing is requested
v1:
- Support for direct trimming without staging
- Support unstaging on kexec (requested by Gregory Lumen)
Roberto Sassu (12):
ima: Remove ima_h_table structure
ima: Replace static htable queue with dynamically allocated array
ima: Introduce per binary measurements list type ima_num_records
counter
ima: Introduce per binary measurements list type binary_runtime_size
value
ima: Introduce _ima_measurements_start() and _ima_measurements_next()
ima: Mediate open/release method of the measurements list
ima: Use snprintf() in create_securityfs_measurement_lists
ima: Introduce ima_dump_measurement()
ima: Add support for staging measurements with prompt
ima: Add support for flushing the hash table when staging measurements
ima: Support staging and deleting N measurements records
doc: security: Add documentation of exporting and deleting IMA
measurements
.../admin-guide/kernel-parameters.txt | 6 +
Documentation/security/IMA-export-delete.rst | 203 ++++++++++
Documentation/security/index.rst | 1 +
MAINTAINERS | 2 +
security/integrity/ima/Kconfig | 15 +
security/integrity/ima/ima.h | 28 +-
security/integrity/ima/ima_api.c | 2 +-
security/integrity/ima/ima_fs.c | 346 ++++++++++++++++--
security/integrity/ima/ima_init.c | 5 +
security/integrity/ima/ima_kexec.c | 42 ++-
security/integrity/ima/ima_queue.c | 327 ++++++++++++++++-
11 files changed, 905 insertions(+), 72 deletions(-)
create mode 100644 Documentation/security/IMA-export-delete.rst
--
2.43.0
^ permalink raw reply
* Re: [PATCH v2] hardening: Default randstruct off with rust for better allmodconfig support
From: Miguel Ojeda @ 2026-06-05 17:22 UTC (permalink / raw)
To: Mark Brown
Cc: Kees Cook, Gustavo A. R. Silva, Paul Moore, James Morris,
Serge E. Hallyn, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg, Alice Ryhl,
Trevor Gross, Danilo Krummrich, linux-hardening,
linux-security-module, linux-kernel, rust-for-linux
In-Reply-To: <20260605-rust-reverse-randstruct-dep-v2-1-93d38023b6f9@kernel.org>
On Fri, Jun 5, 2026 at 6:51 PM Mark Brown <broonie@kernel.org> wrote:
>
> Currently randstruct does not support rust so we have Kconfig dependencies
> which prevent rust being enabled when randstruct is. Unfortunately this
> prevents rust being enabled in allmodconfig, our standard coverage build.
> randstruct gets turned on by default, then the dependency on !RANDSTRUCT
> causes rust to get disabled.
>
> Work around this by disabling randstruct by default if we have a usable
> rust toolchain and rust support for the architecture, circular
> dependencies prevent us directly depending on !RUST. This means we might
> end up with a configuration that disables both rust and randstruct but
> hopefully it's more likely go give the expected result.
>
> Signed-off-by: Mark Brown <broonie@kernel.org>
Thanks Mark!
Kees, Gustavo: applying this would help Mark's testing of Rust in
linux-next, which is important to keep.
An alternative would be to move forward with `RANDSTRUCT` support:
https://lore.kernel.org/rust-for-linux/20260323130224.165738-1-ojeda@kernel.org/
Either the conditional (on the Rust side) or the unconditional
approaches (modifying the C side) should be fine, i.e. whatever
Kees/Gustavo think is best. The unconditional one would make things
easier on the Rust side, but it is a "bigger" change in terms of
impact. We can always start with the conditional one instead.
Cheers,
Miguel
^ permalink raw reply
* [PATCH v2] hardening: Default randstruct off with rust for better allmodconfig support
From: Mark Brown @ 2026-06-05 16:50 UTC (permalink / raw)
To: Kees Cook, Gustavo A. R. Silva, Paul Moore, James Morris,
Serge E. Hallyn, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg, Alice Ryhl,
Trevor Gross, Danilo Krummrich
Cc: linux-hardening, linux-security-module, linux-kernel,
rust-for-linux, Mark Brown
Currently randstruct does not support rust so we have Kconfig dependencies
which prevent rust being enabled when randstruct is. Unfortunately this
prevents rust being enabled in allmodconfig, our standard coverage build.
randstruct gets turned on by default, then the dependency on !RANDSTRUCT
causes rust to get disabled.
Work around this by disabling randstruct by default if we have a usable
rust toolchain and rust support for the architecture, circular
dependencies prevent us directly depending on !RUST. This means we might
end up with a configuration that disables both rust and randstruct but
hopefully it's more likely go give the expected result.
Signed-off-by: Mark Brown <broonie@kernel.org>
---
Changes in v2:
- Add a HAVE_RUST in there too.
- Link to v1: https://patch.msgid.link/20260605-rust-reverse-randstruct-dep-v1-1-45ce9ee8d0d1@kernel.org
---
security/Kconfig.hardening | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
index 86f8768c63d4..923e7710f005 100644
--- a/security/Kconfig.hardening
+++ b/security/Kconfig.hardening
@@ -285,7 +285,7 @@ config CC_HAS_RANDSTRUCT
choice
prompt "Randomize layout of sensitive kernel structures"
- default RANDSTRUCT_FULL if COMPILE_TEST && (GCC_PLUGINS || CC_HAS_RANDSTRUCT)
+ default RANDSTRUCT_FULL if !(RUST_IS_AVAILABLE && HAVE_RUST) && COMPILE_TEST && (GCC_PLUGINS || CC_HAS_RANDSTRUCT)
default RANDSTRUCT_NONE
help
If you enable this, the layouts of structures that are entirely
---
base-commit: e43ffb69e0438cddd72aaa30898b4dc446f664f8
change-id: 20260605-rust-reverse-randstruct-dep-5a504c861128
Best regards,
--
Mark Brown <broonie@kernel.org>
^ permalink raw reply related
* [PATCH] hardening: Default randstruct off with rust for better allmodconfig support
From: Mark Brown @ 2026-06-05 16:01 UTC (permalink / raw)
To: Kees Cook, Gustavo A. R. Silva, Paul Moore, James Morris,
Serge E. Hallyn, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg, Alice Ryhl,
Trevor Gross, Danilo Krummrich
Cc: linux-hardening, linux-security-module, linux-kernel,
rust-for-linux, Mark Brown
Currently randstruct does not support rust so we have Kconfig dependencies
which prevent rust being enabled when randstruct is. Unfortunately this
prevents rust being enabled in allmodconfig, our standard coverage build.
randstruct gets turned on by default, then the dependency on !RANDSTRUCT
causes rust to get disabled.
Work around this by disabling randstruct by default if we have a usable
rust toolchain, circular dependencies prevent us directly depending on
!RUST. This means we might end up with a configuration that disables both
rust and randstruct but hopefully it's more likely go give the expected
result.
Signed-off-by: Mark Brown <broonie@kernel.org>
---
security/Kconfig.hardening | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
index 86f8768c63d4..1677c4f9637b 100644
--- a/security/Kconfig.hardening
+++ b/security/Kconfig.hardening
@@ -285,7 +285,7 @@ config CC_HAS_RANDSTRUCT
choice
prompt "Randomize layout of sensitive kernel structures"
- default RANDSTRUCT_FULL if COMPILE_TEST && (GCC_PLUGINS || CC_HAS_RANDSTRUCT)
+ default RANDSTRUCT_FULL if !RUST_IS_AVAILABLE && COMPILE_TEST && (GCC_PLUGINS || CC_HAS_RANDSTRUCT)
default RANDSTRUCT_NONE
help
If you enable this, the layouts of structures that are entirely
---
base-commit: e43ffb69e0438cddd72aaa30898b4dc446f664f8
change-id: 20260605-rust-reverse-randstruct-dep-5a504c861128
Best regards,
--
Mark Brown <broonie@kernel.org>
^ permalink raw reply related
* Re: [PATCH v6 12/12] doc: security: Add documentation of exporting and deleting IMA measurements
From: Mimi Zohar @ 2026-06-05 15:59 UTC (permalink / raw)
To: Roberto Sassu, corbet, skhan, dmitry.kasatkin, eric.snowberg,
paul, jmorris, serge
Cc: linux-doc, linux-kernel, linux-integrity, linux-security-module,
gregorylumen, chenste, nramas, Roberto Sassu
In-Reply-To: <20260602111401.1706052-13-roberto.sassu@huaweicloud.com>
On Tue, 2026-06-02 at 13:14 +0200, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
>
> Add the documentation of exporting and deleting IMA measurements in
> Documentation/security/IMA-export-delete.rst.
>
> Also add the missing Documentation/security/IMA-templates.rst file in
> MAINTAINERS.
>
> Link: https://github.com/linux-integrity/linux/issues/1
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Thanks, Roberto! Other than the section titled "Remote Attestation Agent
Workflow", the documentation is well written and flows nicely. More details in
the "Remote Attestation Agent Workflow" section.
> ---
> Documentation/security/IMA-export-delete.rst | 190 +++++++++++++++++++
> Documentation/security/index.rst | 1 +
> MAINTAINERS | 2 +
> 3 files changed, 193 insertions(+)
> create mode 100644 Documentation/security/IMA-export-delete.rst
>
> diff --git a/Documentation/security/IMA-export-delete.rst b/Documentation/security/IMA-export-delete.rst
> new file mode 100644
> index 000000000000..a9e1d3f8ed47
> --- /dev/null
> +++ b/Documentation/security/IMA-export-delete.rst
> @@ -0,0 +1,190 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +==================================
> +IMA Measurements Export and Delete
> +==================================
> +
> +
> +Introduction
> +============
> +
> +The IMA measurements list is currently stored in the kernel memory. Memory
> +occupation grows linearly with the number of records, and can become a
> +problem especially in environments with reduced resources.
> +
> +While there is an advantage in keeping the IMA measurements list in kernel
> +memory, so that it is always available for reading from the securityfs
> +interfaces, storing it elsewhere would make it possible to free precious
> +memory for other kernel usage.
> +
> +The IMA measurements list needs to be retained and safely stored for new
> +attestation servers to validate it. Assuming the IMA measurements list is
> +properly saved, storing it outside the kernel does not introduce security
> +issues, since its integrity is anyway protected by the TPM.
> +
> +Hence, the new IMA staging mechanism is introduced to export IMA
> +measurements to user space and delete them from kernel space.
> +
> +Staging consists in atomically moving the current measurements list to a
> +temporary list, so that measurements can be deleted afterwards. The staging
> +operation locks the hot path (racing with addition of new measurements) for
> +a very short time, only for swapping the list pointers. Deletion of the
> +measurements instead is done locklessly, away from the hot path.
> +
> +There are two flavors of the staging mechanism. In the staging with prompt,
> +all current measurements are staged, read and deleted upon confirmation. In
> +the staging and deleting flavor, N measurements are staged from the
> +beginning of the current measurements list and immediately deleted without
> +confirmation.
> +
> +
> +Management of Staged Measurements
> +=================================
> +
> +Since with the staging mechanism measurement records are removed from the
> +kernel, the staged measurements need to be saved in a storage and
> +concatenated together, so that they can be presented to remote attestation
> +agents as if staging was never done. This task can be accomplished by a
> +system service.
> +
> +Coordination is necessary in the case where there are multiple actors
> +requesting measurements to be staged.
> +
> +In the staging with prompt case, the measurement interfaces can be accessed
> +only by one actor (writer) at a time, so the others will get an error until
> +the former closes it. Since the actors don't care about N, when they gain
> +access to the interface, they will get all the staged measurements at the
> +time of their request.
> +
> +In the case of staging and deleting, coordination is more important, since
> +there is the risk that two actors unaware of each other compute the value N
> +on the current measurements list and request IMA to stage N twice.
> +
> +
> +Remote Attestation Agent Workflow
> +=================================
The example below illustrates a narrow use case in which only a single
attestation server is present, eliminating the need to retain the measurement
list records. The recommended general case, however, involves multiple
attestation servers and requires the system service to retain all measurement
records since boot, with the ability to respond with records from any specified
point onward.
Mimi
> +
> +Users can choose the staging method they find more appropriate for their
> +workflow.
> +
> +If, as an example, a remote attestation agent would like to present to the
> +remote attestation server only the measurements that are required to
> +verify the TPM quote, its workflow would be the following.
> +
> +With staging with prompt, the agent stages the current measurements list,
> +reads and stores the measurements in a storage and immediately requests
> +IMA to delete the staged measurements from kernel memory. Afterwards, it
> +calculates N by replaying the PCR extend on the stored measurements until
> +the calculated PCRs match the quoted PCRs. It then keeps the measurements
> +in excess for the next attestation request.
> +
> +At the next attestation request, the agent performs the same steps above,
> +and concatenates the new measurements to the ones in excess from the
> +previous request. Also in this case, the agent replays the PCR extend until
> +it matches the currently quoted PCRs, keeps the measurements in excess and
> +presents the new N measurement records to the remote attestation server.
> +
> +With the staging and deleting method, the agent reads the current
> +measurements list, calculates N and requests IMA to delete only those. The
> +measurements in excess are kept in the IMA measurements list and can be
> +retrieved at the next remote attestation request.
> +
> +
> +Usage
> +=====
> +
> +The IMA staging mechanism can be enabled from the kernel configuration with
> +the CONFIG_IMA_STAGING option. This option prevents inadvertently removing
> +the IMA measurement list on systems which do not properly save it.
> +
> +If the option is enabled, IMA duplicates the current securityfs
> +measurements interfaces (both binary and ASCII), by adding the ``_staged``
> +file suffix. Both the original and the staging interfaces gain the write
> +permission for the root user and group, but require the process to have
> +CAP_SYS_ADMIN set.
> +
> +The staging mechanism supports two flavors.
> +
> +
> +Staging with prompt
> +~~~~~~~~~~~~~~~~~~~
> +
> +The current measurements list is moved to a temporary staging area,
> +allowing it to be saved to external storage, before being deleted upon
> +confirmation.
> +
> +This staging process is achieved with the following steps.
> +
> + 1. ``echo A > <_staged interface>``: the user requests IMA to stage the
> + entire measurements list;
> + 2. ``cat <_staged interface>``: the user reads the staged measurements;
> + 3. ``echo D > <_staged interface>``: the user requests IMA to delete
> + staged measurements.
> +
> +
> +Staging and deleting
> +~~~~~~~~~~~~~~~~~~~~
> +
> +N measurements are staged to a temporary staging area, and immediately
> +deleted without further confirmation.
> +
> +This staging process is achieved with the following steps.
> +
> + 1. ``cat <original interface>``: the user reads the current measurements
> + list and determines what the value N for staging should be;
> + 2. ``echo N > <original interface>``: the user requests IMA to delete N
> + measurements from the current measurements list.
> +
> +
> +Interface Access
> +================
> +
> +In order to avoid the IMA measurements list being suddenly truncated by the
> +staging mechanism during a read, or having multiple concurrent staging, a
> +semaphore-like locking scheme has been implemented on all the measurements
> +list interfaces.
> +
> +Multiple readers can access concurrently the original and staged
> +interfaces, and they can be in mutual exclusion with one writer. In order
> +to see the same state across all the measurement interfaces, the same
> +writer is allowed to open multiple interfaces for write or read/write.
> +
> +If an illegal access occurs, the open to the measurements list interface is
> +denied.
> +
> +
> +Kexec
> +=====
> +
> +In the event a kexec() system call occurs between staging and deleting, the
> +staged measurement records are marshalled before the current measurements
> +list, so that they are both available when the secondary kernel starts.
> +
> +If measurement is suspended before requesting to delete staged or current
> +measurements, IMA returns an error to user space to let it know that
> +marshalling is already in progress, so that it does not save the
> +measurements twice.
> +
> +IMA also disallows staging when suspending measurement, to avoid the
> +situation where neither measurements are carried over to the secondary
> +kernel, nor they are saved by user space to the storage.
> +
> +
> +Hash table
> +==========
> +
> +By default, the template digest of staged measurement records are kept in
> +kernel memory (only template data are freed), to be able to detect
> +duplicate records independently of staging.
> +
> +The new kernel option ``ima_flush_htable`` has been introduced to
> +explicitly request a complete deletion of the staged measurements, for
> +maximum kernel memory saving. If the option has been specified, duplicate
> +records are still avoided on records of the current measurements list,
> +but there can be duplicates between different groups of staged
> +measurements.
> +
> +Flushing the hash table is supported only for the staging with prompt
> +flavor. For the staging and deleting flavor, it would have been necessary
> +to lock the hot path adding new measurements for the time needed to remove
> +each selected measurement individually.
> diff --git a/Documentation/security/index.rst b/Documentation/security/index.rst
> index 3e0a7114a862..00650dcf38cb 100644
> --- a/Documentation/security/index.rst
> +++ b/Documentation/security/index.rst
> @@ -8,6 +8,7 @@ Security Documentation
> credentials
> snp-tdx-threat-model
> IMA-templates
> + IMA-export-delete
> keys/index
> lsm
> lsm-development
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 461a3eed6129..70ff6bae3493 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -12752,6 +12752,8 @@ R: Eric Snowberg <eric.snowberg@oracle.com>
> L: linux-integrity@vger.kernel.org
> S: Supported
> T: git git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity.git
> +F: Documentation/security/IMA-export-delete.rst
> +F: Documentation/security/IMA-templates.rst
> F: include/linux/secure_boot.h
> F: security/integrity/
> F: security/integrity/ima/
^ permalink raw reply
* Re: [PATCH v6 10/12] ima: Add support for flushing the hash table when staging measurements
From: Mimi Zohar @ 2026-06-05 15:28 UTC (permalink / raw)
To: Roberto Sassu, corbet, skhan, dmitry.kasatkin, eric.snowberg,
paul, jmorris, serge
Cc: linux-doc, linux-kernel, linux-integrity, linux-security-module,
gregorylumen, chenste, nramas, Roberto Sassu
In-Reply-To: <20260602111401.1706052-11-roberto.sassu@huaweicloud.com>
On Tue, 2026-06-02 at 13:13 +0200, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
>
> During staging and delete, measurements are not completely deallocated.
> Their entry digest portion is kept and is still reachable with the hash
> table to detect duplicate records. If the number of records is significant,
> this reduces the memory saving benefit of staging.
>
> Some users might be interested in achieving the best memory saving (the
> measurements are completely deallocated) at the cost of having duplicate
> records across the staged measurement lists. Duplicate records are still
> avoided within the current measurement list.
>
> Introduce the new kernel option ima_flush_htable to decide whether or not
> the digests of staged measurement records are flushed from the hash table,
> when they are deleted, to achieve the maximum memory saving.
>
> When the option is enabled, replace the old hash table with a new one,
> by calling ima_alloc_replace_htable(), and completely delete the
> measurements records.
>
> Note: This code derives from the Alt-IMA Huawei project, whose license is
> GPL-2.0 OR MIT.
>
> Link: https://github.com/linux-integrity/linux/issues/1
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> ---
> .../admin-guide/kernel-parameters.txt | 6 +++
> security/integrity/ima/ima.h | 1 +
> security/integrity/ima/ima_queue.c | 41 ++++++++++++++++---
> 3 files changed, 42 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 4d0f545fb3ec..aad318803f82 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2343,6 +2343,12 @@ Kernel parameters
> Use the canonical format for the binary runtime
> measurements, instead of host native format.
>
> + ima_flush_htable [IMA]
> + Flush the IMA hash table when deleting all the
> + staged measurement records, to achieve maximum
> + memory saving at the cost of having duplicate
> + records across the staged measurement lists.
Thank you for patch description, kernel doc, and Kconfig updates.
> +
> ima_hash= [IMA]
> Format: { md5 | sha1 | rmd160 | sha256 | sha384
> | sha512 | ... }
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index a05db5b18982..d2e740c8ff75 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -343,6 +343,7 @@ extern atomic_long_t ima_num_records[BINARY__LAST];
> extern atomic_long_t ima_num_violations;
> extern struct hlist_head __rcu *ima_htable;
> extern struct mutex ima_extend_list_mutex;
> +extern bool ima_flush_htable;
Making ima_flush_htable global is only needed for "[PATCH v6 11/12] ima: Support
staging and deleting N measurements records", not here. Please make it static
here and change it to global as needed.
Mimi
^ permalink raw reply
* Re: [PATCH v2 1/9] security: add LSM blob and hooks for namespaces
From: Mickaël Salaün @ 2026-06-05 15:06 UTC (permalink / raw)
To: Paul Moore, Christian Brauner, Günther Noack,
Serge E . Hallyn
Cc: Daniel Durning, Jonathan Corbet, Justin Suess, Lennart Poettering,
Mikhail Ivanov, Nicolas Bouchinet, Shervin Oloumi, Tingmao Wang,
kernel-team, linux-fsdevel, linux-kernel, linux-security-module
In-Reply-To: <20260527181127.879771-2-mic@digikod.net>
Paul, could you please take a look at this patch and the next one? I'd
like to push it to linux-next to get more feedback.
On Wed, May 27, 2026 at 08:11:14PM +0200, Mickaël Salaün wrote:
> From: Christian Brauner <brauner@kernel.org>
>
> All namespace types now share the same ns_common infrastructure. Extend
> this to include a security blob so LSMs can start managing namespaces
> uniformly without having to add one-off hooks or security fields to
> every individual namespace type.
>
> Add a ns_security pointer to ns_common and the corresponding lbs_ns blob
> size to lsm_blob_sizes. Allocation and freeing hooks are called from the
> common __ns_common_init() and __ns_common_free() paths so every
> namespace type gets covered in one go. All information about the
> namespace type and the appropriate casting helpers to get at the
> containing namespace are available via ns_common making it
> straightforward for LSMs to differentiate when they need to.
>
> A namespace_install hook is called from validate_ns() during setns(2)
> giving LSMs a chance to enforce policy on namespace transitions. The
> LSM check runs before ns->ops->install() so the security module can deny
> the operation before any type-specific installation effects.
>
> Individual namespace types can still have their own specialized security
> hooks when needed. This is just the common baseline that makes it easy
> to track and manage namespaces from the security side without requiring
> every namespace type to reinvent the wheel.
>
> Cc: Günther Noack <gnoack@google.com>
> Cc: Paul Moore <paul@paul-moore.com>
> Cc: Serge E. Hallyn <serge@hallyn.com>
> Signed-off-by: Christian Brauner <brauner@kernel.org>
> Link: https://lore.kernel.org/r/20260216-work-security-namespace-v1-1-075c28758e1f@kernel.org
> Signed-off-by: Mickaël Salaün <mic@digikod.net>
> ---
>
> Changes since v1:
> https://lore.kernel.org/r/20260312100444.2609563-2-mic@digikod.net
> - Move security_namespace_install() before ns->ops->install() in
> validate_ns() (suggested by Christian Brauner).
> - Only call proc_free_inum() on security_namespace_alloc() failure
> when inum was allocated by this function (suggested by Christian
> Brauner).
> - Fix anonymous mount namespace blob leak: move
> security_namespace_free() into __ns_common_free() and make
> proc_free_inum() conditional on dynamically allocated inums
> via MNT_NS_INO_SPECIAL_MAX, so free_mnt_ns() can call
> ns_common_free() unconditionally (suggested by Christian
> Brauner). Also reported by Daniel Durning while working on
> SELinux support for these hooks:
> https://lore.kernel.org/r/20260318201747.4477-1-danieldurning.work@gmail.com
> - Rename security_namespace_alloc() to security_namespace_init()
> to match the caller-name convention and reflect that the hook
> initialises LSM state attached to a constructed ns_common rather
> than allocating the ns_common itself (suggested by Paul Moore).
> - Refine the security_namespace_free() kdoc to clarify that
> RCU-safe blob freeing is required only if an LSM exposes data
> within the blob to concurrent RCU readers, and document that
> the blob memory itself is released with kfree() after the
> namespace_free hooks return (suggested by Paul Moore).
> - Günther Noack's v1 Reviewed-by is not carried forward to v2:
> the validate_ns() reordering and the anonymous-mount-namespace
> blob-leak fix are semantic changes that were not part of his
> review. Cc'd instead.
> ---
> fs/namespace.c | 3 +-
> include/linux/lsm_hook_defs.h | 3 ++
> include/linux/lsm_hooks.h | 1 +
> include/linux/ns/ns_common_types.h | 3 ++
> include/linux/security.h | 20 ++++++++
> include/uapi/linux/nsfs.h | 1 +
> kernel/nscommon.c | 17 ++++++-
> kernel/nsproxy.c | 6 +++
> security/lsm_init.c | 2 +
> security/security.c | 77 ++++++++++++++++++++++++++++++
> 10 files changed, 130 insertions(+), 3 deletions(-)
>
> diff --git a/fs/namespace.c b/fs/namespace.c
> index fe919abd2f01..031ef3fafa48 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -4179,8 +4179,7 @@ static void dec_mnt_namespaces(struct ucounts *ucounts)
>
> static void free_mnt_ns(struct mnt_namespace *ns)
> {
> - if (!is_anon_ns(ns))
> - ns_common_free(ns);
> + ns_common_free(ns);
> dec_mnt_namespaces(ns->ucounts);
> mnt_ns_tree_remove(ns);
> }
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index 2b8dfb35caed..c389ea904392 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -265,6 +265,9 @@ LSM_HOOK(int, -ENOSYS, task_prctl, int option, unsigned long arg2,
> LSM_HOOK(void, LSM_RET_VOID, task_to_inode, struct task_struct *p,
> struct inode *inode)
> LSM_HOOK(int, 0, userns_create, const struct cred *cred)
> +LSM_HOOK(int, 0, namespace_init, struct ns_common *ns)
> +LSM_HOOK(void, LSM_RET_VOID, namespace_free, struct ns_common *ns)
> +LSM_HOOK(int, 0, namespace_install, const struct nsset *nsset, struct ns_common *ns)
> LSM_HOOK(int, 0, ipc_permission, struct kern_ipc_perm *ipcp, short flag)
> LSM_HOOK(void, LSM_RET_VOID, ipc_getlsmprop, struct kern_ipc_perm *ipcp,
> struct lsm_prop *prop)
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index b4f8cad53ddb..5cff13069529 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -112,6 +112,7 @@ struct lsm_blob_sizes {
> unsigned int lbs_ipc;
> unsigned int lbs_key;
> unsigned int lbs_msg_msg;
> + unsigned int lbs_ns;
> unsigned int lbs_perf_event;
> unsigned int lbs_task;
> unsigned int lbs_xattr_count; /* num xattr slots in new_xattrs array */
> diff --git a/include/linux/ns/ns_common_types.h b/include/linux/ns/ns_common_types.h
> index ea45c54e4435..5cfe0ce3c881 100644
> --- a/include/linux/ns/ns_common_types.h
> +++ b/include/linux/ns/ns_common_types.h
> @@ -116,6 +116,9 @@ struct ns_common {
> struct dentry *stashed;
> const struct proc_ns_operations *ops;
> unsigned int inum;
> +#ifdef CONFIG_SECURITY
> + void *ns_security;
> +#endif
> union {
> struct ns_tree;
> struct rcu_head ns_rcu;
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 41d7367cf403..8865f46cc3a9 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -67,6 +67,7 @@ enum fs_value_type;
> struct watch;
> struct watch_notification;
> struct lsm_ctx;
> +struct nsset;
>
> /* Default (no) options for the capable function */
> #define CAP_OPT_NONE 0x0
> @@ -80,6 +81,7 @@ struct lsm_ctx;
>
> struct ctl_table;
> struct audit_krule;
> +struct ns_common;
> struct user_namespace;
> struct timezone;
>
> @@ -540,6 +542,9 @@ int security_task_prctl(int option, unsigned long arg2, unsigned long arg3,
> unsigned long arg4, unsigned long arg5);
> void security_task_to_inode(struct task_struct *p, struct inode *inode);
> int security_create_user_ns(const struct cred *cred);
> +int security_namespace_init(struct ns_common *ns);
> +void security_namespace_free(struct ns_common *ns);
> +int security_namespace_install(const struct nsset *nsset, struct ns_common *ns);
> int security_ipc_permission(struct kern_ipc_perm *ipcp, short flag);
> void security_ipc_getlsmprop(struct kern_ipc_perm *ipcp, struct lsm_prop *prop);
> int security_msg_msg_alloc(struct msg_msg *msg);
> @@ -1430,6 +1435,21 @@ static inline int security_create_user_ns(const struct cred *cred)
> return 0;
> }
>
> +static inline int security_namespace_init(struct ns_common *ns)
> +{
> + return 0;
> +}
> +
> +static inline void security_namespace_free(struct ns_common *ns)
> +{
> +}
> +
> +static inline int security_namespace_install(const struct nsset *nsset,
> + struct ns_common *ns)
> +{
> + return 0;
> +}
> +
> static inline int security_ipc_permission(struct kern_ipc_perm *ipcp,
> short flag)
> {
> diff --git a/include/uapi/linux/nsfs.h b/include/uapi/linux/nsfs.h
> index a25e38d1c874..ea0f0267d90f 100644
> --- a/include/uapi/linux/nsfs.h
> +++ b/include/uapi/linux/nsfs.h
> @@ -55,6 +55,7 @@ enum init_ns_ino {
> MNT_NS_INIT_INO = 0xEFFFFFF8U,
> #ifdef __KERNEL__
> MNT_NS_ANON_INO = 0xEFFFFFF7U,
> + MNT_NS_INO_SPECIAL_MAX = MNT_NS_ANON_INO,
> #endif
> };
>
> diff --git a/kernel/nscommon.c b/kernel/nscommon.c
> index 3166c1fd844a..e72426bba29a 100644
> --- a/kernel/nscommon.c
> +++ b/kernel/nscommon.c
> @@ -4,6 +4,7 @@
> #include <linux/ns_common.h>
> #include <linux/nstree.h>
> #include <linux/proc_ns.h>
> +#include <linux/security.h>
> #include <linux/user_namespace.h>
> #include <linux/vfsdebug.h>
>
> @@ -59,6 +60,9 @@ int __ns_common_init(struct ns_common *ns, u32 ns_type, const struct proc_ns_ope
>
> refcount_set(&ns->__ns_ref, 1);
> ns->stashed = NULL;
> +#ifdef CONFIG_SECURITY
> + ns->ns_security = NULL;
> +#endif
> ns->ops = ops;
> ns->ns_id = 0;
> ns->ns_type = ns_type;
> @@ -77,6 +81,14 @@ int __ns_common_init(struct ns_common *ns, u32 ns_type, const struct proc_ns_ope
> ret = proc_alloc_inum(&ns->inum);
> if (ret)
> return ret;
> +
> + ret = security_namespace_init(ns);
> + if (ret) {
> + if (!inum)
> + proc_free_inum(ns->inum);
> + return ret;
> + }
> +
> /*
> * Tree ref starts at 0. It's incremented when namespace enters
> * active use (installed in nsproxy) and decremented when all
> @@ -91,7 +103,10 @@ int __ns_common_init(struct ns_common *ns, u32 ns_type, const struct proc_ns_ope
>
> void __ns_common_free(struct ns_common *ns)
> {
> - proc_free_inum(ns->inum);
> + security_namespace_free(ns);
> +
> + if (ns->inum > MNT_NS_INO_SPECIAL_MAX)
> + proc_free_inum(ns->inum);
> }
>
> struct ns_common *__must_check ns_owner(struct ns_common *ns)
> diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
> index d9d3d5973bf5..0f1b208d8eef 100644
> --- a/kernel/nsproxy.c
> +++ b/kernel/nsproxy.c
> @@ -385,6 +385,12 @@ static int prepare_nsset(unsigned flags, struct nsset *nsset)
>
> static inline int validate_ns(struct nsset *nsset, struct ns_common *ns)
> {
> + int ret;
> +
> + ret = security_namespace_install(nsset, ns);
> + if (ret)
> + return ret;
> +
> return ns->ops->install(nsset, ns);
> }
>
> diff --git a/security/lsm_init.c b/security/lsm_init.c
> index 7c0fd17f1601..dcd2a228c4f6 100644
> --- a/security/lsm_init.c
> +++ b/security/lsm_init.c
> @@ -303,6 +303,7 @@ static void __init lsm_prepare(struct lsm_info *lsm)
> lsm_blob_size_update(&blobs->lbs_ipc, &blob_sizes.lbs_ipc);
> lsm_blob_size_update(&blobs->lbs_key, &blob_sizes.lbs_key);
> lsm_blob_size_update(&blobs->lbs_msg_msg, &blob_sizes.lbs_msg_msg);
> + lsm_blob_size_update(&blobs->lbs_ns, &blob_sizes.lbs_ns);
> lsm_blob_size_update(&blobs->lbs_perf_event,
> &blob_sizes.lbs_perf_event);
> lsm_blob_size_update(&blobs->lbs_sock, &blob_sizes.lbs_sock);
> @@ -450,6 +451,7 @@ int __init security_init(void)
> lsm_pr("blob(ipc) size %d\n", blob_sizes.lbs_ipc);
> lsm_pr("blob(key) size %d\n", blob_sizes.lbs_key);
> lsm_pr("blob(msg_msg)_size %d\n", blob_sizes.lbs_msg_msg);
> + lsm_pr("blob(ns) size %d\n", blob_sizes.lbs_ns);
> lsm_pr("blob(sock) size %d\n", blob_sizes.lbs_sock);
> lsm_pr("blob(superblock) size %d\n", blob_sizes.lbs_superblock);
> lsm_pr("blob(perf_event) size %d\n", blob_sizes.lbs_perf_event);
> diff --git a/security/security.c b/security/security.c
> index 4e999f023651..21cc45d4bbd0 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -26,6 +26,7 @@
> #include <linux/string.h>
> #include <linux/xattr.h>
> #include <linux/msg.h>
> +#include <linux/ns_common.h>
> #include <linux/overflow.h>
> #include <linux/perf_event.h>
> #include <linux/fs.h>
> @@ -381,6 +382,19 @@ static int lsm_superblock_alloc(struct super_block *sb)
> GFP_KERNEL);
> }
>
> +/**
> + * lsm_ns_alloc - allocate a composite namespace blob
> + * @ns: the namespace that needs a blob
> + *
> + * Allocate the namespace blob for all the modules
> + *
> + * Returns 0, or -ENOMEM if memory can't be allocated.
> + */
> +static int lsm_ns_alloc(struct ns_common *ns)
> +{
> + return lsm_blob_alloc(&ns->ns_security, blob_sizes.lbs_ns, GFP_KERNEL);
> +}
> +
> /**
> * lsm_fill_user_ctx - Fill a user space lsm_ctx structure
> * @uctx: a userspace LSM context to be filled
> @@ -3358,6 +3372,69 @@ int security_create_user_ns(const struct cred *cred)
> return call_int_hook(userns_create, cred);
> }
>
> +/**
> + * security_namespace_init() - Initialize LSM security data for a namespace
> + * @ns: the namespace being initialized
> + *
> + * Initialize the LSM security blob attached to the namespace. The namespace type
> + * is available via ns->ns_type, and the owning user namespace (if any)
> + * via ns->ops->owner(ns).
> + *
> + * Return: Returns 0 if successful, otherwise < 0 error code.
> + */
> +int security_namespace_init(struct ns_common *ns)
> +{
> + int rc;
> +
> + rc = lsm_ns_alloc(ns);
> + if (unlikely(rc))
> + return rc;
> +
> + rc = call_int_hook(namespace_init, ns);
> + if (unlikely(rc))
> + security_namespace_free(ns);
> +
> + return rc;
> +}
> +
> +/**
> + * security_namespace_free() - Release LSM security data from a namespace
> + * @ns: the namespace being freed
> + *
> + * Release security data attached to the namespace. Called before the
> + * namespace structure is freed.
> + *
> + * Note: If an LSM exposes data within the security blob to concurrent
> + * RCU readers, it must use RCU-safe freeing for that data. The blob
> + * memory itself is released with kfree() after the namespace_free
> + * hooks return.
> + */
> +void security_namespace_free(struct ns_common *ns)
> +{
> + if (!ns->ns_security)
> + return;
> +
> + call_void_hook(namespace_free, ns);
> +
> + kfree(ns->ns_security);
> + ns->ns_security = NULL;
> +}
> +
> +/**
> + * security_namespace_install() - Check permission to install a namespace
> + * @nsset: the target nsset being configured
> + * @ns: the namespace being installed
> + *
> + * Check permission before allowing a namespace to be installed into the
> + * process's set of namespaces via setns(2).
> + *
> + * Return: Returns 0 if permission is granted, otherwise < 0 error code.
> + */
> +int security_namespace_install(const struct nsset *nsset, struct ns_common *ns)
> +{
> + return call_int_hook(namespace_install, nsset, ns);
> +}
> +
> /**
> * security_ipc_permission() - Check if sysv ipc access is allowed
> * @ipcp: ipc permission structure
> --
> 2.54.0
>
>
^ permalink raw reply
* Re: [PATCH v6 09/12] ima: Add support for staging measurements with prompt
From: Mimi Zohar @ 2026-06-05 14:57 UTC (permalink / raw)
To: Roberto Sassu, corbet, skhan, dmitry.kasatkin, eric.snowberg,
paul, jmorris, serge
Cc: linux-doc, linux-kernel, linux-integrity, linux-security-module,
gregorylumen, chenste, nramas, Roberto Sassu, Stefan Berger
In-Reply-To: <20260602111401.1706052-10-roberto.sassu@huaweicloud.com>
On Tue, 2026-06-02 at 13:13 +0200, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
>
> Introduce the ability of staging the IMA measurement list and deleting them
> with a prompt.
>
> Staging means moving the current measurement list records to a separate
> location, and allowing users to read and delete it. This causes the current
> measurement list to be emptied (since records were moved) and new
> measurements to be added on the empty list. Staging can be done only once
> at a time. In the event of kexec(), staging is aborted and staged records
> will be carried over to the new kernel.
The kexec locking changes look good, thanks.
>
> Introduce ascii_runtime_measurements_<algo>_staged and
> binary_runtime_measurements_<algo>_staged interfaces to access and delete
> the measurements.
>
> Use 'echo A > <IMA _staged interface>' and
> 'echo D > <IMA _staged interface>' to respectively stage and delete the
> entire measurements list. Locking of these interfaces is also mediated with
> a call to _ima_measurements_open() and with ima_measurements_release().
>
> Implement the staging functionality by introducing the new global
> measurements list ima_measurements_staged, and ima_queue_stage() and
> ima_queue_staged_delete_all() to respectively move measurements from the
> current measurements list to the staged one, and to move staged
> measurements to the ima_measurements_trim list for deletion. Introduce
> ima_queue_delete() to delete the measurements.
>
> Staging is forbidden after measurement is suspended, and between staging
> and deleting, so that walking the staged and current measurements list can
> be done locklessly in ima_dump_measurement_list(). Strict ordering of
> suspending and dumping is enforced by two reboot notifiers with different
> priority. Refusing to delete staged measurements also signals to user space
> that those measurements are already carried over to the secondary kernel,
> so that it does not save them twice.
>
> Finally, introduce the BINARY_STAGED and BINARY_FULL binary measurements
> list types, to maintain the counters and the binary size of staged
> measurements and the full measurements list (including records that were
> staged). BINARY still represents the current binary measurements list.
>
> Use the binary size for the BINARY + BINARY_STAGED types in
> ima_add_kexec_buffer(), since both measurements list types are copied to
> the secondary kernel during kexec. Use BINARY_FULL in
> ima_measure_kexec_event(), to generate a critical data record.
>
> It should be noted that the BINARY_FULL counter is not passed through
> kexec. Thus, the number of records included in the kexec critical data
> records refers to the records since the critical data records generated
> from the previous kexec event.
>
> Note: This code derives from the Alt-IMA Huawei project, whose license is
> GPL-2.0 OR MIT.
>
> Link: https://github.com/linux-integrity/linux/issues/1
> Suggested-by: Gregory Lumen <gregorylumen@linux.microsoft.com> (staging revert)
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> Tested-by: Stefan Berger <stefanb@linux.ibm.com>
Thanks for the updates to the patch description, function docs, and comments.
Just one change needed (below) — otherwise this looks great.
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index c00c133a140f..a05db5b18982 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
[...]
> @@ -337,6 +342,7 @@ extern atomic_long_t ima_num_records[BINARY__LAST];
> /* Total number of violations since hard boot. */
> extern atomic_long_t ima_num_violations;
> extern struct hlist_head __rcu *ima_htable;
> +extern struct mutex ima_extend_list_mutex;
With the kexec locking change in this version, making ima_extend_list_mutex
global isn't necessary.
>
> static inline unsigned int ima_hash_key(u8 *digest)
> {
>
> diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
> index 618694d5c082..a1aa141756e1 100644
> --- a/security/integrity/ima/ima_queue.c
> +++ b/security/integrity/ima/ima_queue.c
[...]
> @@ -42,11 +43,11 @@ atomic_long_t ima_num_violations = ATOMIC_LONG_INIT(0);
> /* key: inode (before secure-hashing a file) */
> struct hlist_head __rcu *ima_htable;
>
> -/* mutex protects atomicity of extending measurement list
> +/* mutex protects atomicity of extending and staging measurement list
> * and extending the TPM PCR aggregate. Since tpm_extend can take
> * long (and the tpm driver uses a mutex), we can't use the spinlock.
> */
> -static DEFINE_MUTEX(ima_extend_list_mutex);
> +DEFINE_MUTEX(ima_extend_list_mutex);
Please drop this change.
Mimi
^ permalink raw reply
* [PATCH v6 4/4] tpm: tpm_crb_ffa: revert defered_probed when tpm_crb_ffa is built-in
From: Yeoreum Yun @ 2026-06-05 14:43 UTC (permalink / raw)
To: linux-security-module, linux-kernel, linux-integrity
Cc: paul, zohar, roberto.sassu, noodles, jarkko, sudeep.holla,
jmorris, serge, dmitry.kasatkin, eric.snowberg, jgg, Yeoreum Yun
In-Reply-To: <20260605144325.434436-1-yeoreum.yun@arm.com>
commit 746d9e9f62a6 ("tpm: tpm_crb_ffa: try to probe tpm_crb_ffa when it's built-in")
probe tpm_crb_ffa forcefully when it's built-in to integrate with IMA.
However, IMA now provides the IMA_INIT_LATE_SYNC build option, which
initialises IMA at the late_initcall_sync level, so this change is no
longer required.
Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
drivers/char/tpm/tpm_crb_ffa.c | 18 +++---------------
1 file changed, 3 insertions(+), 15 deletions(-)
diff --git a/drivers/char/tpm/tpm_crb_ffa.c b/drivers/char/tpm/tpm_crb_ffa.c
index 99f1c1e5644b..025c4d4b17ca 100644
--- a/drivers/char/tpm/tpm_crb_ffa.c
+++ b/drivers/char/tpm/tpm_crb_ffa.c
@@ -177,23 +177,13 @@ static int tpm_crb_ffa_to_linux_errno(int errno)
*/
int tpm_crb_ffa_init(void)
{
- int ret = 0;
-
- if (!IS_MODULE(CONFIG_TCG_ARM_CRB_FFA)) {
- ret = ffa_register(&tpm_crb_ffa_driver);
- if (ret) {
- tpm_crb_ffa = ERR_PTR(-ENODEV);
- return ret;
- }
- }
-
if (!tpm_crb_ffa)
- ret = -ENOENT;
+ return -ENOENT;
if (IS_ERR_VALUE(tpm_crb_ffa))
- ret = -ENODEV;
+ return -ENODEV;
- return ret;
+ return 0;
}
EXPORT_SYMBOL_GPL(tpm_crb_ffa_init);
@@ -405,9 +395,7 @@ static struct ffa_driver tpm_crb_ffa_driver = {
.id_table = tpm_crb_ffa_device_id,
};
-#ifdef MODULE
module_ffa_driver(tpm_crb_ffa_driver);
-#endif
MODULE_AUTHOR("Arm");
MODULE_DESCRIPTION("TPM CRB FFA driver");
--
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
^ permalink raw reply related
* [PATCH v6 3/4] security: ima: rename boot_aggregate when ima is initialised at late_sync
From: Yeoreum Yun @ 2026-06-05 14:43 UTC (permalink / raw)
To: linux-security-module, linux-kernel, linux-integrity
Cc: paul, zohar, roberto.sassu, noodles, jarkko, sudeep.holla,
jmorris, serge, dmitry.kasatkin, eric.snowberg, jgg,
Jonathan McDowell, Yeoreum Yun
In-Reply-To: <20260605144325.434436-1-yeoreum.yun@arm.com>
From: Jonathan McDowell <noodles@meta.com>
The Linux IMA (Integrity Measurement Architecture) subsystem used for
secure boot, file integrity, or remote attestation cannot be a loadable
module for few reasons listed below:
o Boot-Time Integrity: IMA’s main role is to measure and appraise files
before they are used. This includes measuring critical system files
during early boot (e.g., init, init scripts, login binaries). If IMA
were a module, it would be loaded too late to cover those.
o TPM Dependency: IMA integrates tightly with the TPM to record
measurements into PCRs. The TPM must be initialized early (ideally
before init_ima()), which aligns with IMA being built-in.
o Security Model: IMA is part of a Trusted Computing Base (TCB). Making
it a module would weaken the security model, as a potentially
compromised system could delay or tamper with its initialization.
IMA must be built-in to ensure it starts measuring from the earliest
possible point in boot which inturn implies TPM must be initialised and
ready to use before IMA.
Unfortunately some TPM drivers (such as Arm FF-A, or SPI attached TPM
devices) are not reliably available during the initcall_late stage,
resulting in a log error:
ima: No TPM chip found, activating TPM-bypass!
To address this issue, IMA_INIT_LATE_SYNC is introduced.
However, a remote attestation service cannot determine when IMA has been
initialized because the boot_aggregate measurement name remains unchanged,
even though IMA is initialized later at late_initcall_sync when
IMA_INIT_LATE_SYNC is enabled.
Therefore, use a distinct boot_aggregate name when IMA_INIT_LATE_SYNC
is enabled, allowing the remote attestation service to identify
when IMA has been initialized.
Signed-off-by: Jonathan McDowell <noodles@meta.com>
[yeoreum.yun@arm.com: modified to align with the IMA_INIT_LATE_SYNC change]
Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
---
security/integrity/ima/ima.h | 1 +
security/integrity/ima/ima_init.c | 15 +++++++++++----
security/integrity/ima/ima_template_lib.c | 3 ++-
3 files changed, 14 insertions(+), 5 deletions(-)
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 69e9bf0b82c6..194b195cec1e 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -66,6 +66,7 @@ extern struct ima_algo_desc *ima_algo_array __ro_after_init;
extern int ima_appraise;
extern struct tpm_chip *ima_tpm_chip;
extern const char boot_aggregate_name[];
+extern const char boot_aggregate_late_name[];
/* IMA event related data */
struct ima_event_data {
diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
index a2f34f2d8ad7..4c24bd535466 100644
--- a/security/integrity/ima/ima_init.c
+++ b/security/integrity/ima/ima_init.c
@@ -22,6 +22,7 @@
/* name for boot aggregate entry */
const char boot_aggregate_name[] = "boot_aggregate";
+const char boot_aggregate_late_name[] = "boot_aggregate_late";
struct tpm_chip *ima_tpm_chip;
/* Add the boot aggregate to the IMA measurement list and extend
@@ -45,11 +46,11 @@ static int __init ima_add_boot_aggregate(void)
const char *audit_cause = "ENOMEM";
struct ima_template_entry *entry;
struct ima_iint_cache tmp_iint, *iint = &tmp_iint;
- struct ima_event_data event_data = { .iint = iint,
- .filename = boot_aggregate_name };
+ struct ima_event_data event_data = { .iint = iint };
struct ima_max_digest_data hash;
struct ima_digest_data *hash_hdr = container_of(&hash.hdr,
struct ima_digest_data, hdr);
+ const char *filename;
int result = -ENOMEM;
int violation = 0;
@@ -59,6 +60,12 @@ static int __init ima_add_boot_aggregate(void)
iint->ima_hash->algo = ima_hash_algo;
iint->ima_hash->length = hash_digest_size[ima_hash_algo];
+ if (IS_ENABLED(CONFIG_IMA_INIT_LATE_SYNC))
+ filename = boot_aggregate_late_name;
+ else
+ filename = boot_aggregate_name;
+ event_data.filename = filename;
+
/*
* With TPM 2.0 hash agility, TPM chips could support multiple TPM
* PCR banks, allowing firmware to configure and enable different
@@ -86,7 +93,7 @@ static int __init ima_add_boot_aggregate(void)
}
result = ima_store_template(entry, violation, NULL,
- boot_aggregate_name,
+ filename,
CONFIG_IMA_MEASURE_PCR_IDX);
if (result < 0) {
ima_free_template_entry(entry);
@@ -95,7 +102,7 @@ static int __init ima_add_boot_aggregate(void)
}
return 0;
err_out:
- integrity_audit_msg(AUDIT_INTEGRITY_PCR, NULL, boot_aggregate_name, op,
+ integrity_audit_msg(AUDIT_INTEGRITY_PCR, NULL, filename, op,
audit_cause, result, 0);
return result;
}
diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c
index 0e627eac9c33..8a89236f926c 100644
--- a/security/integrity/ima/ima_template_lib.c
+++ b/security/integrity/ima/ima_template_lib.c
@@ -363,7 +363,8 @@ int ima_eventdigest_init(struct ima_event_data *event_data,
goto out;
}
- if ((const char *)event_data->filename == boot_aggregate_name) {
+ if ((const char *)event_data->filename == boot_aggregate_name ||
+ (const char *)event_data->filename == boot_aggregate_late_name) {
if (ima_tpm_chip) {
hash.hdr.algo = HASH_ALGO_SHA1;
result = ima_calc_boot_aggregate(hash_hdr);
--
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
^ permalink raw reply related
* [PATCH v6 2/4] security: ima: introduce IMA_INIT_LATE_SYNC option
From: Yeoreum Yun @ 2026-06-05 14:43 UTC (permalink / raw)
To: linux-security-module, linux-kernel, linux-integrity
Cc: paul, zohar, roberto.sassu, noodles, jarkko, sudeep.holla,
jmorris, serge, dmitry.kasatkin, eric.snowberg, jgg, Yeoreum Yun
In-Reply-To: <20260605144325.434436-1-yeoreum.yun@arm.com>
To generate the boot_aggregate log in the IMA subsystem with
TPM PCR values, the TPM driver must be built as built-in and
must be probed before the IMA subsystem is initialized.
However, when the TPM device operates over the FF-A protocol using
the CRB interface, probing fails and returns -EPROBE_DEFER if
the tpm_crb_ffa device — an FF-A device that provides the communication
interface to the tpm_crb driver — has not yet been probed.
To ensure the TPM device operating over the FF-A protocol with
the CRB interface is probed before IMA initialization,
the following conditions must be met:
1. The corresponding ffa_device must be registered,
which is done via ffa_init().
2. The tpm_crb_driver must successfully probe this device via
tpm_crb_ffa_init().
3. The tpm_crb driver using CRB over FF-A can then
be probed successfully. (See crb_acpi_add() and
tpm_crb_ffa_init() for reference.)
Unfortunately, ffa_init(), tpm_crb_ffa_init(), and crb_acpi_driver_init()
are all registered with device_initcall, which means
crb_acpi_driver_init() may be invoked before ffa_init() and
tpm_crb_ffa_init() are completed.
When this occurs, probing the TPM device is deferred.
However, the deferred probe can happen after the IMA subsystem
has already been initialized, since IMA initialization is performed
during late_initcall, and deferred_probe_initcall() is performed
at the same level.
And the similar situation is reported on TPM devices attached on SPI
bus[0].
To resolve this, introduce IMA_INIT_LATE_SYNC option to initialise
IMA at late_inicall_sync so that IMA is initialized with the TPM
device probed deferred.
When this option is enabled, modules that access files in the
initramfs through usermode helper calls such as request_module()
during initcall must not be built-in. Otherwise, IMA may miss
measuring those files [1].
Link: https://lore.kernel.org/all/aYXEepLhUouN5f99@earth.li/ [0]
Link: https://lore.kernel.org/all/2b3782398cc17ce9d355490a0c42ebce9120a9ae.camel@linux.ibm.com/ [1]
Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
---
security/integrity/ima/Kconfig | 10 ++++++++++
security/integrity/ima/ima_main.c | 4 ++++
2 files changed, 14 insertions(+)
diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 862fbee2b174..75f71401fba3 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -332,4 +332,14 @@ config IMA_KEXEC_EXTRA_MEMORY_KB
If set to the default value of 0, an extra half page of memory for those
additional measurements will be allocated.
+config IMA_INIT_LATE_SYNC
+ bool "Initialise IMA at late_initcall_sync"
+ default n
+ help
+ This option initialises IMA at late_initcall_sync for platforms
+ where TPM device probing is deferred.
+ When this option is enabled, modules that access files in the
+ initramfs through usermode helper calls such as request_module()
+ during initcall must not be built-in. Otherwise, IMA may miss
+ file measurements for them.
endif
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 5cea53fc36df..1cfae4b83dc5 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -1337,5 +1337,9 @@ DEFINE_LSM(ima) = {
.order = LSM_ORDER_LAST,
.blobs = &ima_blob_sizes,
/* Start IMA after the TPM is available */
+#ifndef CONFIG_IMA_INIT_LATE_SYNC
.initcall_late = init_ima,
+#else
+ .initcall_late_sync = init_ima,
+#endif
};
--
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
^ permalink raw reply related
* [PATCH v6 1/4] security: lsm: allow LSMs to register for late_initcall_sync init
From: Yeoreum Yun @ 2026-06-05 14:43 UTC (permalink / raw)
To: linux-security-module, linux-kernel, linux-integrity
Cc: paul, zohar, roberto.sassu, noodles, jarkko, sudeep.holla,
jmorris, serge, dmitry.kasatkin, eric.snowberg, jgg, Yeoreum Yun
In-Reply-To: <20260605144325.434436-1-yeoreum.yun@arm.com>
There are situations where LSMs have dependencies that might mean they
want to be initialised later in the boot process, to ensure those
dependencies are available. In particular there are some TPM setups (Arm
FF-A devices, SPI attached TPMs) required by IMA which are not
guaranteed to be initialised for regular initcall_late.
Add an initcall_late_sync option that can be used in these situations.
Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
---
include/linux/lsm_hooks.h | 2 ++
security/lsm_init.c | 13 +++++++++++--
2 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index b4f8cad53ddb..c4488c4a6d8a 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -167,6 +167,7 @@ enum lsm_order {
* @initcall_fs: LSM callback for fs_initcall setup, optional
* @initcall_device: LSM callback for device_initcall() setup, optional
* @initcall_late: LSM callback for late_initcall() setup, optional
+ * @initcall_late_sync: LSM callback for late_initcall_sync() setup, optional
*/
struct lsm_info {
const struct lsm_id *id;
@@ -182,6 +183,7 @@ struct lsm_info {
int (*initcall_fs)(void);
int (*initcall_device)(void);
int (*initcall_late)(void);
+ int (*initcall_late_sync)(void);
};
#define DEFINE_LSM(lsm) \
diff --git a/security/lsm_init.c b/security/lsm_init.c
index 7c0fd17f1601..a1ad641811de 100644
--- a/security/lsm_init.c
+++ b/security/lsm_init.c
@@ -556,13 +556,22 @@ device_initcall(security_initcall_device);
* security_initcall_late - Run the LSM late initcalls
*/
static int __init security_initcall_late(void)
+{
+ return lsm_initcall(late);
+}
+late_initcall(security_initcall_late);
+
+/**
+ * security_initcall_late_sync - Run the LSM late initcalls sync
+ */
+static int __init security_initcall_late_sync(void)
{
int rc;
- rc = lsm_initcall(late);
+ rc = lsm_initcall(late_sync);
lsm_pr_dbg("all enabled LSMs fully activated\n");
call_blocking_lsm_notifier(LSM_STARTED_ALL, NULL);
return rc;
}
-late_initcall(security_initcall_late);
+late_initcall_sync(security_initcall_late_sync);
--
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
^ permalink raw reply related
* [PATCH v6 0/4] introduce IMA_INIT_LATE_SYNC option
From: Yeoreum Yun @ 2026-06-05 14:43 UTC (permalink / raw)
To: linux-security-module, linux-kernel, linux-integrity
Cc: paul, zohar, roberto.sassu, noodles, jarkko, sudeep.holla,
jmorris, serge, dmitry.kasatkin, eric.snowberg, jgg, Yeoreum Yun
To generate the boot_aggregate log in the IMA subsystem with TPM PCR values,
the TPM driver must be built as built-in and
must be probed before the IMA subsystem is initialized.
However, when the TPM device operates over the FF-A protocol using
the CRB interface, probing fails and returns -EPROBE_DEFER if
the tpm_crb_ffa device — an FF-A device that provides the communication
interface to the tpm_crb driver — has not yet been probed.
To ensure the TPM device operating over the FF-A protocol with
the CRB interface is probed before IMA initialization,
the following conditions must be met:
1. The corresponding ffa_device must be registered,
which is done via ffa_init().
2. The tpm_crb_driver must successfully probe this device via
tpm_crb_ffa_init().
3. The tpm_crb driver using CRB over FF-A can then
be probed successfully. (See crb_acpi_add() and
tpm_crb_ffa_init() for reference.)
Unfortunately, ffa_init(), tpm_crb_ffa_init(), and crb_acpi_driver_init() are
all registered with device_initcall, which means crb_acpi_driver_init() may
be invoked before ffa_init() and tpm_crb_ffa_init() are completed.
When this occurs, probing the TPM device is deferred.
However, the deferred probe can happen after the IMA subsystem
has already been initialized, since IMA initialization is performed
during late_initcall, and deferred_probe_initcall() is performed
at the same level.
And the similar situation is reported on TPM devices attached on SPI
bus[0].
To resolve this, introduce IMA_INIT_LATE_SYNC option to initialise
IMA at late_inicall_sync so that IMA is initialized with the TPM
device probed defered.
When this option is enabled, modules that access files in the
initramfs through usermode helper calls such as request_module()
during initcall must not be built-in. Otherwise, IMA may miss
measuring those files since they're the file accesses before the
initialisation of IMA [1].
Link: https://lore.kernel.org/all/aYXEepLhUouN5f99@earth.li/ [0]
Link: https://lore.kernel.org/all/2b3782398cc17ce9d355490a0c42ebce9120a9ae.camel@linux.ibm.com/ [1]
Patch history
=============
from v5 to v6:
- add rb tag and missing SOB.
- https://lore.kernel.org/all/20260601142749.3379697-1-yeoreum.yun@arm.com/
from v4 to v5:
- rebase on v7.1-rc6
- apply boot_aggreate name patch from @Jonathan and align it with
IMA_INIT_LATE_SYNC option.
- https://lore.kernel.org/all/20260525075404.3480282-1-yeoreum.yun@arm.com/
from v3 to v4:
- rebase on v7.1-rc5
- introduce IMA_INIT_LATE_SYNC option to control IMA initailisation.
- https://lore.kernel.org/all/cover.1777036497.git.noodles@meta.com/
from v2 to v3:
- Drop ff-a/pKVM diff (this seems to have a separate set of
discussion)
- Rework IMA delayed initialisation to avoid delaying when unnecessary
- Ensure IMA log clearly indicates when we've initialised late
- https://lore.kernel.org/all/20260422162449.1814615-1-yeoreum.yun@arm.com/
from v1 to v2:
- add notifier to make ffa-driver pkvm initialised.
- modify to try initailisation again when IMA coudln't find proper TPM device.
- https://lore.kernel.org/all/20260417175759.3191279-1-yeoreum.yun@arm.com/#t
Jonathan McDowell (1):
security: ima: rename boot_aggregate when ima is initialised at
late_sync
Yeoreum Yun (3):
security: lsm: allow LSMs to register for late_initcall_sync init
security: ima: introduce IMA_INIT_LATE_SYNC option
tpm: tpm_crb_ffa: revert defered_probed when tpm_crb_ffa is built-in
drivers/char/tpm/tpm_crb_ffa.c | 18 +++---------------
include/linux/lsm_hooks.h | 2 ++
security/integrity/ima/Kconfig | 10 ++++++++++
security/integrity/ima/ima.h | 1 +
security/integrity/ima/ima_init.c | 15 +++++++++++----
security/integrity/ima/ima_main.c | 4 ++++
security/integrity/ima/ima_template_lib.c | 3 ++-
security/lsm_init.c | 13 +++++++++++--
8 files changed, 44 insertions(+), 22 deletions(-)
base-commit: e43ffb69e0438cddd72aaa30898b4dc446f664f8
--
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
^ permalink raw reply
* Re: -next status as at v7.1-rc6
From: Serge E. Hallyn @ 2026-06-05 13:45 UTC (permalink / raw)
To: Linus Torvalds
Cc: Paul Moore, linux-security-module, Mark Brown, Blaise Boscaccy,
Alexei Starovoitov, linux-next, linux-kernel
In-Reply-To: <CAHk-=wij4nkMRcshzEGsxvjwP2RBQyaiQ4-vQrYTOqvQusxu9g@mail.gmail.com>
On Thu, Jun 04, 2026 at 04:18:46PM -0700, Linus Torvalds wrote:
> On Thu, 4 Jun 2026 at 15:23, Paul Moore <paul@paul-moore.com> wrote:
> >
> > While you didn't reply to any of my comments explaining how Hornet
> > works, specifically how it ties into the kernel, I'm assuming you've
> > read the overview. Can you help those of us in the LSM space
> > understand why a BPF dev's NACK on code that lives strictly under
> > security/ is sufficient grounds to reject an LSM patch?
>
> Honestly, I'm not competent to make a judgment call between two
> different models for hash chain verification, so I basically *have* to
> go by maintainer opinions.
>
> And the discussions I have been cc'd on have not been what I'd call
> enlightening.
>
> But people have pointed out that the LSM code mucks around with bpf
> internals, and those NAK's have had reasons for them.
>
> And honestly, I don't understand *why* Hornet does what it does - and
> does it in ways that obviously annoy the bpf people. There is no
> *reason* to look at the bpf maps that I can see, and from my
> understanding of Alexei's arguments (which may be lacking), the fact
> that Hornet does that is the main reason for the NAK.
The two most useful threads I believe were from a year ago,
20250502184421.1424368-1-bboscaccy@linux.microsoft.com
and
20250528215037.2081066-1-bboscaccy@linux.microsoft.com
which includes the proposal by the BPF side:
https://lore.kernel.org/linux-security-module/CACYkzJ6VQUExfyt0=-FmXz46GHJh3d=FXh5j4KfexcEFbHV-vg@mail.gmail.com/
There were 2 or three objections from each side iiuc, but the main ones
that stuck in my mind were
1. whether it is ok to rely on a signed userspace bpf verifier program to
verify the signature.
2. objection by James Bottomley
(2f71d6c03698eb17d51f7247efde777627ee578a.camel@HansenPartnership.com)
about the verifiability of the hash chain link.
> But instead of working with the bpf people on coming up with some
> model that does *not* do that, it all seems to have become a "we'll do
> it anyway, despite maintainer complaints".
>
> And I *did* see the bpf people pointing to "this would be an
> acceptable alternative" with KP Singh outlining something that *had*
> been discussed.
>
> But I never actually saw anybody say "ok, we'll try that instead".
>
> Maybe I missed it.
>
> But from what I saw, it really looked like "I see NAK's from three
> different bpf maintainers, with suggested alternate approaches". None
> of which resulted in anything that looked like "ok, we'll try to
> follow your guidance", only more of the same.
>
> Why would *my* input then make any difference?
>
> The bpf people's arguments resonated more with me. For example, the
> whole "we need to know if it passed the bpf signature" seems to be
> complate pointless silliness, and the bpf peoples responses to that
> resonated with me. There's *no* point in any LSM check whether the
> signature passed or not, since if it didn't pass, it's not getting
> loaded.
>
> So that's basically where I stand - I've seen disagreement, and I've
> seen what looks to me like reasonable push-back, and I've not really
> seen the LSM response as taking it into account.
>
> Linus
^ permalink raw reply
* Re: [PATCH] keys: prevent slab cache merging for key_jar
From: Vlastimil Babka (SUSE) @ 2026-06-05 12:16 UTC (permalink / raw)
To: Mohammed EL Kadiri, David Howells, Jarkko Sakkinen
Cc: Paul Moore, James Morris, Serge E . Hallyn, Kees Cook,
Vlastimil Babka, keyrings, linux-security-module, linux-hardening,
linux-kernel
In-Reply-To: <20260604125034.13757-1-med08elkadiri@gmail.com>
On 6/4/26 14:50, Mohammed EL Kadiri wrote:
> The key_jar slab cache holds struct key objects containing cryptographic
> keys, authentication tokens, and keyring linkage. This cache currently
> lacks merge prevention, allowing the SLUB allocator to merge it with
> other similarly-sized caches.
>
> On a default Ubuntu 6.17.0-23-generic system, key_jar has 5 aliases,
> meaning 5 unrelated object types share its slab pages. struct key is
> 224 bytes, placed in 256-byte slabs alongside biovec-16, maple_node,
> ip6_dst_cache, task_delay_info, and kmalloc-256 users.
>
> Cross-cache heap exploitation is a well-documented attack class
> (CVE-2022-29582, CVE-2022-2588, CVE-2021-22555) where slab cache
> merging enables type confusion between unrelated kernel objects. A
> use-after-free in any subsystem sharing slab pages with key_jar could
> allow an attacker to reclaim a freed slot as a struct key, or corrupt
> an existing key through a dangling pointer to a different type.
>
> Add SLAB_NO_MERGE to ensure key_jar receives dedicated slab pages,
> eliminating cross-cache attacks targeting struct key. The memory
> overhead is minimal: with 32 objects per slab page and typical key
> usage bounded by system keyring size, the cost of dedicated pages is
> negligible. There is zero performance impact on the allocation hot
> path.
>
> This follows the precedent set by skbuff_head_cache (net/core/skbuff.c)
> which uses SLAB_NO_MERGE for similar isolation requirements.
>
> Signed-off-by: Mohammed EL Kadiri <med08elkadiri@gmail.com>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
> ---
> security/keys/key.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/security/keys/key.c b/security/keys/key.c
> index 3bbdde778631..592b65cf8539 100644
> --- a/security/keys/key.c
> +++ b/security/keys/key.c
> @@ -1275,7 +1275,7 @@ void __init key_init(void)
> {
> /* allocate a slab in which we can store keys */
> key_jar = kmem_cache_create("key_jar", sizeof(struct key),
> - 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
> + 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_NO_MERGE, NULL);
>
> /* add the special key types */
> list_add_tail(&key_type_keyring.link, &key_types_list);
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