[PATCH v5 00/13] ima: Introduce staging mechanism

[PATCH v5 00/13] ima: Introduce staging mechanism

[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 entries, 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 components.

Storing the IMA measurements list 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 allow user space
to remove the desired portion of the measurements list from the kernel.


Usage
=====

The IMA staging mechanism can be enabled from the kernel configuration
with the CONFIG_IMA_STAGING option.

If it is enabled, IMA duplicates the current 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, and
staged measurements are deleted upon confirmation.

This staging process is achieved with the following steps.

  1.  echo A > <original 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 entries are removed from
the kernel, the user needs to save the staged ones in a storage and
concatenate them together, so that it can present them to remote
attestation agents as if staging was never done.


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 avoids
measurements entries to be stored twice if there is contention between the
measurements interfaces and kexec. Patch 13 adds the documentation of the
staging mechanism.


Changelog
=========

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 (13):
  ima: Remove ima_h_table structure
  ima: Replace static htable queue with dynamically allocated array
  ima: Introduce per binary measurements list type ima_num_entries
    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 entries
  ima: Return error on deleting measurements already copied during kexec
  doc: security: Add documentation of the IMA staging mechanism

 .../admin-guide/kernel-parameters.txt         |   4 +
 Documentation/security/IMA-staging.rst        | 163 +++++++++
 Documentation/security/index.rst              |   1 +
 MAINTAINERS                                   |   2 +
 security/integrity/ima/Kconfig                |  16 +
 security/integrity/ima/ima.h                  |  32 +-
 security/integrity/ima/ima_api.c              |   2 +-
 security/integrity/ima/ima_fs.c               | 315 ++++++++++++++++--
 security/integrity/ima/ima_init.c             |   5 +
 security/integrity/ima/ima_kexec.c            |  53 ++-
 security/integrity/ima/ima_queue.c            | 283 ++++++++++++++--
 11 files changed, 803 insertions(+), 73 deletions(-)
 create mode 100644 Documentation/security/IMA-staging.rst

-- 
2.43.0

[PATCH v5 01/13] ima: Remove ima_h_table structure

[Roberto Sassu]

From: Roberto Sassu <roberto.sassu@huawei.com>

With the upcoming change of dynamically allocating and replacing the hash
table, the ima_h_table structure would have been replaced with a new one.

However, since the ima_h_table structure contains also the counters for
number of measurements entries and violations, we would have needed to
preserve their values in the new ima_h_table structure.

Instead, 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       |  9 +++------
 security/integrity/ima/ima_api.c   |  2 +-
 security/integrity/ima/ima_fs.c    | 19 +++++++++----------
 security/integrity/ima/ima_kexec.c |  2 +-
 security/integrity/ima/ima_queue.c | 17 ++++++++++-------
 5 files changed, 24 insertions(+), 25 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 69e9bf0b82c6..51a8a582df56 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -324,12 +324,9 @@ 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;
+extern atomic_long_t ima_num_entries;
+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..aaa460d70ff7 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,
 };
 
@@ -64,7 +63,7 @@ static ssize_t ima_show_measurements_count(struct file *filp,
 					   char __user *buf,
 					   size_t count, loff_t *ppos)
 {
-	return ima_show_htable_value(buf, count, ppos, &ima_htable.len);
+	return ima_show_counter(buf, count, ppos, &ima_num_entries);
 
 }
 
@@ -545,7 +544,7 @@ 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..5801649fbbef 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_entries);
 
 	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..1f6515f7d015 100644
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -32,11 +32,14 @@ static unsigned long binary_runtime_size;
 static unsigned long binary_runtime_size = ULONG_MAX;
 #endif
 
+/* num of stored measurements in the list */
+atomic_long_t ima_num_entries = ATOMIC_LONG_INIT(0);
+/* num of violations in the list */
+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 +64,7 @@ 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 +116,10 @@ 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_entries);
 	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

[PATCH v5 02/13] ima: Replace static htable queue with dynamically allocated array

[Roberto Sassu]

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>
---
 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 51a8a582df56..94bf890628e5 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);
@@ -326,7 +327,7 @@ extern spinlock_t ima_queue_lock;
 
 extern atomic_long_t ima_num_entries;
 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 1f6515f7d015..41f4941ceaad 100644
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -38,9 +38,7 @@ atomic_long_t ima_num_entries = 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
@@ -54,17 +52,53 @@ 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)) {
@@ -104,6 +138,7 @@ 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);
@@ -116,10 +151,13 @@ 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_entries);
 	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

[PATCH v5 03/13] ima: Introduce per binary measurements list type ima_num_entries counter

[Roberto Sassu]

From: Roberto Sassu <roberto.sassu@huawei.com>

Make ima_num_entries 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>
---
 security/integrity/ima/ima.h       | 9 ++++++++-
 security/integrity/ima/ima_fs.c    | 3 +--
 security/integrity/ima/ima_kexec.c | 2 +-
 security/integrity/ima/ima_queue.c | 7 +++++--
 4 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 94bf890628e5..b417c9d792d8 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
@@ -325,7 +332,7 @@ int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
  */
 extern spinlock_t ima_queue_lock;
 
-extern atomic_long_t ima_num_entries;
+extern atomic_long_t ima_num_entries[BINARY__LAST];
 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 aaa460d70ff7..79b0f287c668 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -63,8 +63,7 @@ static ssize_t ima_show_measurements_count(struct file *filp,
 					   char __user *buf,
 					   size_t count, loff_t *ppos)
 {
-	return ima_show_counter(buf, count, ppos, &ima_num_entries);
-
+	return ima_show_counter(buf, count, ppos, &ima_num_entries[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 5801649fbbef..40962dc0ca86 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_entries);
+	len = atomic_long_read(&ima_num_entries[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 41f4941ceaad..952172a4905d 100644
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -33,7 +33,10 @@ static unsigned long binary_runtime_size = ULONG_MAX;
 #endif
 
 /* num of stored measurements in the list */
-atomic_long_t ima_num_entries = ATOMIC_LONG_INIT(0);
+atomic_long_t ima_num_entries[BINARY__LAST] = {
+	[0 ... BINARY__LAST - 1] = ATOMIC_LONG_INIT(0)
+};
+
 /* num of violations in the list */
 atomic_long_t ima_num_violations = ATOMIC_LONG_INIT(0);
 
@@ -154,7 +157,7 @@ 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_entries);
+	atomic_long_inc(&ima_num_entries[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

[PATCH v5 04/13] ima: Introduce per binary measurements list type binary_runtime_size value

[Roberto Sassu]

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 b417c9d792d8..f8ab6b604c0d 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 40962dc0ca86..44ebefbdcab0 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_entries[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 952172a4905d..b6d10dceb669 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
 
 /* num of stored measurements in the list */
@@ -131,6 +133,20 @@ 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.
@@ -163,13 +179,7 @@ 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;
 }
 
@@ -178,12 +188,18 @@ 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

[PATCH v5 05/13] ima: Introduce _ima_measurements_start() and _ima_measurements_next()

[Roberto Sassu]

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.

Link: https://github.com/linux-integrity/linux/issues/1
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.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 79b0f287c668..9a8dba14d82a 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

[PATCH v5 06/13] ima: Mediate open/release method of the measurements list

[Roberto Sassu]

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 open by multiple readers, or alternatively by a single
writer.

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 | 71 +++++++++++++++++++++++++++++++--
 1 file changed, 67 insertions(+), 4 deletions(-)

diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index 9a8dba14d82a..68edea7139d5 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -25,6 +25,8 @@
 #include "ima.h"
 
 static DEFINE_MUTEX(ima_write_mutex);
+static DEFINE_MUTEX(ima_measure_mutex);
+static long ima_measure_users;
 
 bool ima_canonical_fmt;
 static int __init default_canonical_fmt_setup(char *str)
@@ -209,16 +211,76 @@ static const struct seq_operations ima_measurments_seqops = {
 	.show = ima_measurements_show
 };
 
+static int ima_measure_lock(bool write)
+{
+	mutex_lock(&ima_measure_mutex);
+	if ((write && ima_measure_users != 0) ||
+	    (!write && ima_measure_users < 0)) {
+		mutex_unlock(&ima_measure_mutex);
+		return -EBUSY;
+	}
+
+	if (write)
+		ima_measure_users--;
+	else
+		ima_measure_users++;
+	mutex_unlock(&ima_measure_mutex);
+	return 0;
+}
+
+static void ima_measure_unlock(bool write)
+{
+	mutex_lock(&ima_measure_mutex);
+	if (write)
+		ima_measure_users++;
+	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 +345,15 @@ 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

[PATCH v5 07/13] ima: Use snprintf() in create_securityfs_measurement_lists

[Roberto Sassu]

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>
---
 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 68edea7139d5..7709a4576322 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -472,11 +472,13 @@ 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);
@@ -484,11 +486,13 @@ 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

[PATCH v5 08/13] ima: Introduce ima_dump_measurement()

[Roberto Sassu]

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>
---
 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 44ebefbdcab0..d7d0fb639d99 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

[PATCH v5 09/13] ima: Add support for staging measurements with prompt

[Roberto Sassu]

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 content of the measurement list to a
separate location, and allowing users to read and delete it. This causes
the measurement list to be atomically truncated before new measurements can
be added. Staging can be done only once at a time. In the event of kexec(),
staging is reverted and staged entries 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. Also, add write permission to the original measurement
interfaces.

Use 'echo A > <IMA original 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.

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 entries 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 entries included in the kexec critical data
records refers to the entries since the previous kexec 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
Suggested-by: Gregory Lumen <gregorylumen@linux.microsoft.com> (staging revert)
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
 security/integrity/ima/Kconfig     |  13 +++
 security/integrity/ima/ima.h       |   8 +-
 security/integrity/ima/ima_fs.c    | 181 ++++++++++++++++++++++++++---
 security/integrity/ima/ima_kexec.c |  24 +++-
 security/integrity/ima/ima_queue.c |  97 +++++++++++++++-
 5 files changed, 302 insertions(+), 21 deletions(-)

diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 862fbee2b174..48c906793efb 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -332,4 +332,17 @@ 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 y
+	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 reverted and staged measurements are prepended
+	  to the current measurements list when measurements are copied to the
+	  secondary kernel.
+
 endif
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index f8ab6b604c0d..ca8fa43ec72b 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);
@@ -335,6 +340,7 @@ extern spinlock_t ima_queue_lock;
 extern atomic_long_t ima_num_entries[BINARY__LAST];
 extern atomic_long_t ima_num_violations;
 extern struct hlist_head __rcu *ima_htable;
+extern struct mutex ima_extend_list_mutex;
 
 static inline unsigned int ima_hash_key(u8 *digest)
 {
diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index 7709a4576322..088d5a69aa92 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;
@@ -97,6 +104,11 @@ 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)
 {
@@ -118,6 +130,12 @@ 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)
 {
 }
@@ -211,6 +229,13 @@ 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);
@@ -276,9 +301,78 @@ 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 (*ppos > 0 || 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_write(struct file *file, const char __user *buf,
+				      size_t datalen, loff_t *ppos)
+{
+	return _ima_measurements_write(file, buf, datalen, ppos, false);
+}
+
+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,
+	.write = ima_measurements_write,
+	.llseek = seq_lseek,
+	.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,
 };
@@ -352,6 +446,29 @@ static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
 static const struct file_operations ima_ascii_measurements_ops = {
 	.open = ima_ascii_measurements_open,
 	.read = seq_read,
+	.write = ima_measurements_write,
+	.llseek = seq_lseek,
+	.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,
 };
@@ -459,10 +576,20 @@ 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;
+	mode_t permissions = (S_IRUSR | S_IRGRP | S_IWUSR | S_IWGRP);
+	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;
+		file_suffix = "_staged";
+	}
+
 	if (ima_sha1_idx >= NR_BANKS(ima_tpm_chip))
 		count++;
 
@@ -473,29 +600,32 @@ 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);
 	}
@@ -503,6 +633,23 @@ 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
  */
@@ -595,7 +742,13 @@ 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 d7d0fb639d99..064cfce0c318 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_entries[BINARY]);
+	buf_size = ima_get_binary_runtime_size(BINARY_FULL);
+	len = atomic_long_read(&ima_num_entries[BINARY_FULL]);
 
 	n = scnprintf(ima_kexec_event, IMA_KEXEC_EVENT_LEN,
 		      "kexec_segment_size=%lu;ima_binary_runtime_size=%lu;"
@@ -106,13 +106,28 @@ 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) {
+	/*
+	 * It can race with ima_queue_stage() and ima_queue_staged_delete_all().
+	 */
+	mutex_lock(&ima_extend_list_mutex);
+
+	list_for_each_entry_rcu(qe, &ima_measurements_staged, later,
+				lockdep_is_held(&ima_extend_list_mutex)) {
 		ret = ima_dump_measurement(&khdr, qe);
 		if (ret < 0)
 			break;
 	}
 
+	list_for_each_entry_rcu(qe, &ima_measurements, later,
+				lockdep_is_held(&ima_extend_list_mutex)) {
+		if (!ret)
+			ret = ima_dump_measurement(&khdr, qe);
+		if (ret < 0)
+			break;
+	}
+
+	mutex_unlock(&ima_extend_list_mutex);
+
 	/*
 	 * fill in reserved space with some buffer details
 	 * (eg. version, buffer size, number of measurements)
@@ -167,6 +182,7 @@ 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 b6d10dceb669..50519ed837d4 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
@@ -45,11 +46,11 @@ 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);
 
 /*
  * Used internally by the kernel to suspend measurements.
@@ -174,12 +175,16 @@ static int ima_add_digest_entry(struct ima_template_entry *entry,
 				lockdep_is_held(&ima_extend_list_mutex));
 
 	atomic_long_inc(&ima_num_entries[BINARY]);
+	atomic_long_inc(&ima_num_entries[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;
 }
 
@@ -280,6 +285,94 @@ int ima_add_template_entry(struct ima_template_entry *entry, int violation,
 	return result;
 }
 
+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;
+	}
+
+	list_replace(&ima_measurements, &ima_measurements_staged);
+	INIT_LIST_HEAD(&ima_measurements);
+
+	atomic_long_set(&ima_num_entries[BINARY_STAGED],
+			atomic_long_read(&ima_num_entries[BINARY]));
+	atomic_long_set(&ima_num_entries[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);
+
+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;
+	}
+
+	list_replace(&ima_measurements_staged, &ima_measurements_trim);
+	INIT_LIST_HEAD(&ima_measurements_staged);
+
+	atomic_long_set(&ima_num_entries[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;
+}
+
+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

[PATCH v5 10/13] ima: Add support for flushing the hash table when staging measurements

[Roberto Sassu]

From: Roberto Sassu <roberto.sassu@huawei.com>

Introduce the new kernel option ima_flush_htable to decide whether or not
the digests of staged measurement entries are flushed from the hash table,
when they are deleted.

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 entries.

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         |  4 +++
 security/integrity/ima/ima.h                  |  1 +
 security/integrity/ima/ima_queue.c            | 36 ++++++++++++++++---
 3 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 4d0f545fb3ec..56efb8bfcc4e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2343,6 +2343,10 @@ 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 entries.
+
 	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 ca8fa43ec72b..4af66c1de4dc 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -341,6 +341,7 @@ extern atomic_long_t ima_num_entries[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;
 
 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 50519ed837d4..f5c18acfbc43 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
 
+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;
 
@@ -317,10 +331,11 @@ 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);
 
 int ima_queue_staged_delete_all(void)
 {
+	struct hlist_head *old_queue = NULL;
 	LIST_HEAD(ima_measurements_trim);
 
 	mutex_lock(&ima_extend_list_mutex);
@@ -337,13 +352,26 @@ 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;
 }
 
-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;
@@ -365,7 +393,7 @@ 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

[PATCH v5 11/13] ima: Support staging and deleting N measurements entries

[Roberto Sassu]

From: Roberto Sassu <roberto.sassu@huawei.com>

Add support for sending a value N between 1 and ULONG_MAX to the IMA
original measurement interface. This value represents the number of
measurements that should be deleted from the current measurements list. In
this case, measurements are staged in an internal non-user visible list,
and immediately deleted.

This staging method allows the remote attestation agents to easily separate
the measurements that were verified (staged and deleted) from those that
weren't due to the race between taking a TPM quote and reading the
measurements list.

In order to minimize the locking time of ima_extend_list_mutex, deleting
N entries is realized by doing a lockless walk in the current measurements
list to determine the N-th entry to cut, to cut the current measurements
list under the lock, and by deleting the excess entries after releasing the
lock.

Flushing the hash table is not supported for N entries, since it would
require removing the N entries one by one from the hash table under the
ima_extend_list_mutex lock, which would increase the locking time.

The ima_extend_list_mutex lock is necessary in ima_dump_measurement_list()
because ima_queue_delete_partial() uses __list_cut_position() to modify
ima_measurements, for which no RCU-safe variant exists. For the staging
with prompt flavor alone, list_replace_rcu() could have been used instead,
but since both flavors share the same kexec serialization path, the mutex
is required regardless.

Link: https://github.com/linux-integrity/linux/issues/1
Suggested-by: Steven Chen <chenste@linux.microsoft.com>
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
 security/integrity/ima/Kconfig     |  3 +++
 security/integrity/ima/ima.h       |  1 +
 security/integrity/ima/ima_fs.c    | 21 ++++++++++++++-
 security/integrity/ima/ima_kexec.c |  3 ++-
 security/integrity/ima/ima_queue.c | 43 ++++++++++++++++++++++++++++++
 5 files changed, 69 insertions(+), 2 deletions(-)

diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 48c906793efb..4f4373859a4f 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -341,6 +341,9 @@ config IMA_STAGING
 	  It allows user space to stage the measurements list for deletion and
 	  to delete the staged measurements after confirmation.
 
+	  Or, alternatively, it allows user space to specify N measurements
+	  entries to stage internally, so that they can be immediately deleted.
+
 	  On kexec, staging is reverted and staged measurements are prepended
 	  to the current measurements list when measurements are copied to the
 	  secondary kernel.
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 4af66c1de4dc..9a741b33d524 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -320,6 +320,7 @@ 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_queue_delete_partial(unsigned long req_value);
 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 088d5a69aa92..6843dc203b54 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -28,6 +28,7 @@
  * Requests:
  * 'A\n': stage the entire measurements list
  * 'D\n': delete all staged measurements
+ * '[1, ULONG_MAX]\n' delete N measurements entries
  */
 #define STAGED_REQ_LENGTH 21
 
@@ -312,6 +313,7 @@ static ssize_t _ima_measurements_write(struct file *file,
 				       loff_t *ppos, bool staged_interface)
 {
 	char req[STAGED_REQ_LENGTH];
+	unsigned long req_value;
 	int ret;
 
 	if (*ppos > 0 || datalen < 2 || datalen > STAGED_REQ_LENGTH)
@@ -339,7 +341,24 @@ static ssize_t _ima_measurements_write(struct file *file,
 		ret = ima_queue_staged_delete_all();
 		break;
 	default:
-		ret = -EINVAL;
+		if (staged_interface)
+			return -EINVAL;
+
+		if (ima_flush_htable) {
+			pr_debug("Deleting staged N measurements not supported when flushing the hash table is requested\n");
+			return -EINVAL;
+		}
+
+		ret = kstrtoul(req, 10, &req_value);
+		if (ret < 0)
+			return ret;
+
+		if (req_value == 0) {
+			pr_debug("Must delete at least one entry\n");
+			return -EINVAL;
+		}
+
+		ret = ima_queue_delete_partial(req_value);
 	}
 
 	if (ret < 0)
diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index 064cfce0c318..e7bde3d917b2 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -107,7 +107,8 @@ static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
 	memset(&khdr, 0, sizeof(khdr));
 	khdr.version = 1;
 	/*
-	 * It can race with ima_queue_stage() and ima_queue_staged_delete_all().
+	 * It can race with ima_queue_stage(), ima_queue_staged_delete_all()
+	 * and ima_queue_delete_partial().
 	 */
 	mutex_lock(&ima_extend_list_mutex);
 
diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
index f5c18acfbc43..64c4fe73dd5f 100644
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -371,6 +371,49 @@ int ima_queue_staged_delete_all(void)
 	return 0;
 }
 
+int ima_queue_delete_partial(unsigned long req_value)
+{
+	unsigned long req_value_copy = req_value;
+	unsigned long size_to_remove = 0, num_to_remove = 0;
+	LIST_HEAD(ima_measurements_trim);
+	struct ima_queue_entry *qe;
+	int ret = 0;
+
+	/*
+	 * Safe to walk without rcu_read_lock(): single-writer
+	 * exclusion in ima_fs.c prevents any concurrent modification
+	 * to ima_measurements during this walk.
+	 */
+	list_for_each_entry_rcu(qe, &ima_measurements, later, true) {
+		size_to_remove += get_binary_runtime_size(qe->entry);
+		num_to_remove++;
+
+		if (--req_value_copy == 0)
+			break;
+	}
+
+	/* Not enough entries to delete. */
+	if (req_value_copy > 0)
+		return -ENOENT;
+
+	mutex_lock(&ima_extend_list_mutex);
+	/*
+	 * qe remains valid because ima_fs.c enforces single-writer exclusion.
+	 */
+	__list_cut_position(&ima_measurements_trim, &ima_measurements,
+			    &qe->later);
+
+	atomic_long_sub(num_to_remove, &ima_num_entries[BINARY]);
+
+	if (IS_ENABLED(CONFIG_IMA_KEXEC))
+		binary_runtime_size[BINARY] -= size_to_remove;
+
+	mutex_unlock(&ima_extend_list_mutex);
+
+	ima_queue_delete(&ima_measurements_trim, false);
+	return ret;
+}
+
 static void ima_queue_delete(struct list_head *head, bool flush_htable)
 {
 	struct ima_queue_entry *qe, *qe_tmp;
-- 
2.43.0

[PATCH v5 12/13] ima: Return error on deleting measurements already copied during kexec

[Roberto Sassu]

From: Roberto Sassu <roberto.sassu@huawei.com>

Refuse to delete staged or active list measurements, if a kexec racing with
the deletion already copied those measurements in the kexec buffer. In this
way, user space becomes aware that those measurements are going to appear
in the secondary kernel, and thus they don't have to be saved twice.

Link: https://github.com/linux-integrity/linux/issues/1
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
 security/integrity/ima/ima.h       |  5 +++++
 security/integrity/ima/ima_kexec.c |  6 ++++++
 security/integrity/ima/ima_queue.c | 17 +++++++++++++++++
 3 files changed, 28 insertions(+)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 9a741b33d524..9be4c35d7ec1 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -344,6 +344,11 @@ extern struct hlist_head __rcu *ima_htable;
 extern struct mutex ima_extend_list_mutex;
 extern bool ima_flush_htable;
 
+#define IMA_MEASUREMENTS_STAGED_COPIED 1
+#define IMA_MEASUREMENTS_COPIED 2
+
+extern u8 ima_copied_flags;
+
 static inline unsigned int ima_hash_key(u8 *digest)
 {
 	/* there is no point in taking a hash of part of a digest */
diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index e7bde3d917b2..5c7abde114f2 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -119,6 +119,9 @@ static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
 			break;
 	}
 
+	if (!list_empty(&ima_measurements_staged))
+		ima_copied_flags |= IMA_MEASUREMENTS_STAGED_COPIED;
+
 	list_for_each_entry_rcu(qe, &ima_measurements, later,
 				lockdep_is_held(&ima_extend_list_mutex)) {
 		if (!ret)
@@ -127,6 +130,9 @@ static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
 			break;
 	}
 
+	if (!list_empty(&ima_measurements))
+		ima_copied_flags |= IMA_MEASUREMENTS_COPIED;
+
 	mutex_unlock(&ima_extend_list_mutex);
 
 	/*
diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
index 64c4fe73dd5f..7f09cce53772 100644
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -72,6 +72,13 @@ DEFINE_MUTEX(ima_extend_list_mutex);
  */
 static bool ima_measurements_suspended;
 
+/*
+ * Used to determine if staged or active list measurements were copied during
+ * kexec, so that an error can be sent to user space during deletion, and they
+ * don't store those measurements twice.
+ */
+u8 ima_copied_flags;
+
 /* Callers must call synchronize_rcu() and free the hash table. */
 static struct hlist_head *ima_alloc_replace_htable(void)
 {
@@ -344,6 +351,11 @@ int ima_queue_staged_delete_all(void)
 		return -ENOENT;
 	}
 
+	if (ima_copied_flags & IMA_MEASUREMENTS_STAGED_COPIED) {
+		mutex_unlock(&ima_extend_list_mutex);
+		return -ESTALE;
+	}
+
 	list_replace(&ima_measurements_staged, &ima_measurements_trim);
 	INIT_LIST_HEAD(&ima_measurements_staged);
 
@@ -397,6 +409,11 @@ int ima_queue_delete_partial(unsigned long req_value)
 		return -ENOENT;
 
 	mutex_lock(&ima_extend_list_mutex);
+	if (ima_copied_flags & IMA_MEASUREMENTS_COPIED) {
+		mutex_unlock(&ima_extend_list_mutex);
+		return -ESTALE;
+	}
+
 	/*
 	 * qe remains valid because ima_fs.c enforces single-writer exclusion.
 	 */
-- 
2.43.0

[PATCH v5 13/13] doc: security: Add documentation of the IMA staging mechanism

[Roberto Sassu]

From: Roberto Sassu <roberto.sassu@huawei.com>

Add the documentation of the IMA staging mechanism in
Documentation/security/IMA-staging.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>
---
 Documentation/security/IMA-staging.rst | 163 +++++++++++++++++++++++++
 Documentation/security/index.rst       |   1 +
 MAINTAINERS                            |   2 +
 3 files changed, 166 insertions(+)
 create mode 100644 Documentation/security/IMA-staging.rst

diff --git a/Documentation/security/IMA-staging.rst b/Documentation/security/IMA-staging.rst
new file mode 100644
index 000000000000..de6428893f0e
--- /dev/null
+++ b/Documentation/security/IMA-staging.rst
@@ -0,0 +1,163 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==================================
+IMA Measurements Staging Mechanism
+==================================
+
+
+Introduction
+============
+
+The IMA measurements list is currently stored in the kernel memory. Memory
+occupation grows linearly with the number of entries, 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 components.
+
+Storing the IMA measurements list 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 allow user space
+to remove the desired portion of the measurements list from the kernel.
+
+
+Usage
+=====
+
+The IMA staging mechanism can be enabled from the kernel configuration with
+the CONFIG_IMA_STAGING option.
+
+If it is enabled, IMA duplicates the current 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, and
+staged measurements are deleted upon confirmation.
+
+This staging process is achieved with the following steps.
+
+ 1. ``echo A > <original 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 be 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.
+
+If an illegal access occurs, the open to the measurements list interface is
+denied.
+
+
+Management of Staged Measurements
+=================================
+
+Since with the staging mechanism measurement entries are removed from the
+kernel, the user needs to save the staged ones in a storage and concatenate
+them together, so that it can present them to remote attestation agents as
+if staging was never done.
+
+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
+=================================
+
+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 measurements entries 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.
+
+Kexec
+=====
+
+In the event a kexec() system call occurs between staging and deleting, the
+staged measurements entries are prepended to the current measurements list,
+so that they are both available when the secondary kernel starts. In that
+case, IMA returns an error to the user when attempting to delete staged
+measurements to notify about their copy to the kexec buffer, so that the
+user does not store them twice.
+
+
+Hash table
+==========
+
+By default, the template digest of staged measurement entries are kept in
+kernel memory (only template data are freed), to be able to detect
+duplicate entries 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
+entries are still avoided on entries 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..cec064dc1c83 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-staging
    keys/index
    lsm
    lsm-development
diff --git a/MAINTAINERS b/MAINTAINERS
index 2fb1c75afd16..5bc816ab4a5b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -12740,6 +12740,8 @@ 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-staging.rst
+F:	Documentation/security/IMA-templates.rst
 F:	include/linux/secure_boot.h
 F:	security/integrity/
 F:	security/integrity/ima/
-- 
2.43.0

Re: [PATCH v5 09/13] ima: Add support for staging measurements with prompt

[Roberto Sassu]

On Wed, 2026-04-29 at 18:03 +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 content of the measurement list to a
> separate location, and allowing users to read and delete it. This causes
> the measurement list to be atomically truncated before new measurements can
> be added. Staging can be done only once at a time. In the event of kexec(),
> staging is reverted and staged entries 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. Also, add write permission to the original measurement
> interfaces.
> 
> Use 'echo A > <IMA original 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().

While doing the staging in the original interface looks more intuitive,
since it is interface the user operates on, it causes loss of
transaction atomicity.

An agent opening the original interface has to close it, open the
staged interface to read and delete the staged measurement. Other
agents can open the staged interface first and do operations the
original agent didn't intend to do.

Will restore the previous behavior of staging/reading/deleting on the
staged interface. Will keep deleting N entries on the original
interface, since there is no risk of races.

Roberto

> 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.
> 
> 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 entries 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 entries included in the kexec critical data
> records refers to the entries since the previous kexec 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
> Suggested-by: Gregory Lumen <gregorylumen@linux.microsoft.com> (staging revert)
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> ---
>  security/integrity/ima/Kconfig     |  13 +++
>  security/integrity/ima/ima.h       |   8 +-
>  security/integrity/ima/ima_fs.c    | 181 ++++++++++++++++++++++++++---
>  security/integrity/ima/ima_kexec.c |  24 +++-
>  security/integrity/ima/ima_queue.c |  97 +++++++++++++++-
>  5 files changed, 302 insertions(+), 21 deletions(-)
> 
> diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
> index 862fbee2b174..48c906793efb 100644
> --- a/security/integrity/ima/Kconfig
> +++ b/security/integrity/ima/Kconfig
> @@ -332,4 +332,17 @@ 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 y
> +	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 reverted and staged measurements are prepended
> +	  to the current measurements list when measurements are copied to the
> +	  secondary kernel.
> +
>  endif
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index f8ab6b604c0d..ca8fa43ec72b 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);
> @@ -335,6 +340,7 @@ extern spinlock_t ima_queue_lock;
>  extern atomic_long_t ima_num_entries[BINARY__LAST];
>  extern atomic_long_t ima_num_violations;
>  extern struct hlist_head __rcu *ima_htable;
> +extern struct mutex ima_extend_list_mutex;
>  
>  static inline unsigned int ima_hash_key(u8 *digest)
>  {
> diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
> index 7709a4576322..088d5a69aa92 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;
> @@ -97,6 +104,11 @@ 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)
>  {
> @@ -118,6 +130,12 @@ 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)
>  {
>  }
> @@ -211,6 +229,13 @@ 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);
> @@ -276,9 +301,78 @@ 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 (*ppos > 0 || 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_write(struct file *file, const char __user *buf,
> +				      size_t datalen, loff_t *ppos)
> +{
> +	return _ima_measurements_write(file, buf, datalen, ppos, false);
> +}
> +
> +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,
> +	.write = ima_measurements_write,
> +	.llseek = seq_lseek,
> +	.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,
>  };
> @@ -352,6 +446,29 @@ static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
>  static const struct file_operations ima_ascii_measurements_ops = {
>  	.open = ima_ascii_measurements_open,
>  	.read = seq_read,
> +	.write = ima_measurements_write,
> +	.llseek = seq_lseek,
> +	.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,
>  };
> @@ -459,10 +576,20 @@ 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;
> +	mode_t permissions = (S_IRUSR | S_IRGRP | S_IWUSR | S_IWGRP);
> +	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;
> +		file_suffix = "_staged";
> +	}
> +
>  	if (ima_sha1_idx >= NR_BANKS(ima_tpm_chip))
>  		count++;
>  
> @@ -473,29 +600,32 @@ 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);
>  	}
> @@ -503,6 +633,23 @@ 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
>   */
> @@ -595,7 +742,13 @@ 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 d7d0fb639d99..064cfce0c318 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_entries[BINARY]);
> +	buf_size = ima_get_binary_runtime_size(BINARY_FULL);
> +	len = atomic_long_read(&ima_num_entries[BINARY_FULL]);
>  
>  	n = scnprintf(ima_kexec_event, IMA_KEXEC_EVENT_LEN,
>  		      "kexec_segment_size=%lu;ima_binary_runtime_size=%lu;"
> @@ -106,13 +106,28 @@ 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) {
> +	/*
> +	 * It can race with ima_queue_stage() and ima_queue_staged_delete_all().
> +	 */
> +	mutex_lock(&ima_extend_list_mutex);
> +
> +	list_for_each_entry_rcu(qe, &ima_measurements_staged, later,
> +				lockdep_is_held(&ima_extend_list_mutex)) {
>  		ret = ima_dump_measurement(&khdr, qe);
>  		if (ret < 0)
>  			break;
>  	}
>  
> +	list_for_each_entry_rcu(qe, &ima_measurements, later,
> +				lockdep_is_held(&ima_extend_list_mutex)) {
> +		if (!ret)
> +			ret = ima_dump_measurement(&khdr, qe);
> +		if (ret < 0)
> +			break;
> +	}
> +
> +	mutex_unlock(&ima_extend_list_mutex);
> +
>  	/*
>  	 * fill in reserved space with some buffer details
>  	 * (eg. version, buffer size, number of measurements)
> @@ -167,6 +182,7 @@ 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 b6d10dceb669..50519ed837d4 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
> @@ -45,11 +46,11 @@ 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);
>  
>  /*
>   * Used internally by the kernel to suspend measurements.
> @@ -174,12 +175,16 @@ static int ima_add_digest_entry(struct ima_template_entry *entry,
>  				lockdep_is_held(&ima_extend_list_mutex));
>  
>  	atomic_long_inc(&ima_num_entries[BINARY]);
> +	atomic_long_inc(&ima_num_entries[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;
>  }
>  
> @@ -280,6 +285,94 @@ int ima_add_template_entry(struct ima_template_entry *entry, int violation,
>  	return result;
>  }
>  
> +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;
> +	}
> +
> +	list_replace(&ima_measurements, &ima_measurements_staged);
> +	INIT_LIST_HEAD(&ima_measurements);
> +
> +	atomic_long_set(&ima_num_entries[BINARY_STAGED],
> +			atomic_long_read(&ima_num_entries[BINARY]));
> +	atomic_long_set(&ima_num_entries[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);
> +
> +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;
> +	}
> +
> +	list_replace(&ima_measurements_staged, &ima_measurements_trim);
> +	INIT_LIST_HEAD(&ima_measurements_staged);
> +
> +	atomic_long_set(&ima_num_entries[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;
> +}
> +
> +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;

Re: [PATCH v5 11/13] ima: Support staging and deleting N measurements entries

[steven chen]

On 4/29/2026 9:03 AM, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
>
> Add support for sending a value N between 1 and ULONG_MAX to the IMA
> original measurement interface. This value represents the number of
> measurements that should be deleted from the current measurements list. In
> this case, measurements are staged in an internal non-user visible list,
> and immediately deleted.
>
> This staging method allows the remote attestation agents to easily separate
> the measurements that were verified (staged and deleted) from those that
> weren't due to the race between taking a TPM quote and reading the
> measurements list.
>
> In order to minimize the locking time of ima_extend_list_mutex, deleting
> N entries is realized by doing a lockless walk in the current measurements
> list to determine the N-th entry to cut, to cut the current measurements
> list under the lock, and by deleting the excess entries after releasing the
> lock.
>
> Flushing the hash table is not supported for N entries, since it would
> require removing the N entries one by one from the hash table under the
> ima_extend_list_mutex lock, which would increase the locking time.
>
> The ima_extend_list_mutex lock is necessary in ima_dump_measurement_list()
> because ima_queue_delete_partial() uses __list_cut_position() to modify
> ima_measurements, for which no RCU-safe variant exists. For the staging
> with prompt flavor alone, list_replace_rcu() could have been used instead,
> but since both flavors share the same kexec serialization path, the mutex
> is required regardless.

This submit provides two ways for trimming logs:
     Patch 9: stage and delete
     This patch 11: stage and delete N

Both are doing the same thing in different ways

I think the best way is just keep the patch 11 for following reasons:
     Kernel list lock time is minimum
Kernel code change will be much simpler (almost half gone)
User space processing for log trimming is much simpler
no need to maintain two lists (old and staged) in user space
No two lists seen from user space (same as before)
no staged list shown

Steven

> Link: https://github.com/linux-integrity/linux/issues/1
> Suggested-by: Steven Chen <chenste@linux.microsoft.com>
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> ---
>   security/integrity/ima/Kconfig     |  3 +++
>   security/integrity/ima/ima.h       |  1 +
>   security/integrity/ima/ima_fs.c    | 21 ++++++++++++++-
>   security/integrity/ima/ima_kexec.c |  3 ++-
>   security/integrity/ima/ima_queue.c | 43 ++++++++++++++++++++++++++++++
>   5 files changed, 69 insertions(+), 2 deletions(-)
>
> diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
> index 48c906793efb..4f4373859a4f 100644
> --- a/security/integrity/ima/Kconfig
> +++ b/security/integrity/ima/Kconfig
> @@ -341,6 +341,9 @@ config IMA_STAGING
>   	  It allows user space to stage the measurements list for deletion and
>   	  to delete the staged measurements after confirmation.
>   
> +	  Or, alternatively, it allows user space to specify N measurements
> +	  entries to stage internally, so that they can be immediately deleted.
> +
>   	  On kexec, staging is reverted and staged measurements are prepended
>   	  to the current measurements list when measurements are copied to the
>   	  secondary kernel.
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index 4af66c1de4dc..9a741b33d524 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -320,6 +320,7 @@ 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_queue_delete_partial(unsigned long req_value);
>   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 088d5a69aa92..6843dc203b54 100644
> --- a/security/integrity/ima/ima_fs.c
> +++ b/security/integrity/ima/ima_fs.c
> @@ -28,6 +28,7 @@
>    * Requests:
>    * 'A\n': stage the entire measurements list
>    * 'D\n': delete all staged measurements
> + * '[1, ULONG_MAX]\n' delete N measurements entries
>    */
>   #define STAGED_REQ_LENGTH 21
>   
> @@ -312,6 +313,7 @@ static ssize_t _ima_measurements_write(struct file *file,
>   				       loff_t *ppos, bool staged_interface)
>   {
>   	char req[STAGED_REQ_LENGTH];
> +	unsigned long req_value;
>   	int ret;
>   
>   	if (*ppos > 0 || datalen < 2 || datalen > STAGED_REQ_LENGTH)
> @@ -339,7 +341,24 @@ static ssize_t _ima_measurements_write(struct file *file,
>   		ret = ima_queue_staged_delete_all();
>   		break;
>   	default:
> -		ret = -EINVAL;
> +		if (staged_interface)
> +			return -EINVAL;
> +
> +		if (ima_flush_htable) {
> +			pr_debug("Deleting staged N measurements not supported when flushing the hash table is requested\n");
> +			return -EINVAL;
> +		}
> +
> +		ret = kstrtoul(req, 10, &req_value);
> +		if (ret < 0)
> +			return ret;
> +
> +		if (req_value == 0) {
> +			pr_debug("Must delete at least one entry\n");
> +			return -EINVAL;
> +		}
> +
> +		ret = ima_queue_delete_partial(req_value);
>   	}
>   
>   	if (ret < 0)
> diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
> index 064cfce0c318..e7bde3d917b2 100644
> --- a/security/integrity/ima/ima_kexec.c
> +++ b/security/integrity/ima/ima_kexec.c
> @@ -107,7 +107,8 @@ static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
>   	memset(&khdr, 0, sizeof(khdr));
>   	khdr.version = 1;
>   	/*
> -	 * It can race with ima_queue_stage() and ima_queue_staged_delete_all().
> +	 * It can race with ima_queue_stage(), ima_queue_staged_delete_all()
> +	 * and ima_queue_delete_partial().
>   	 */
>   	mutex_lock(&ima_extend_list_mutex);
>   
> diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
> index f5c18acfbc43..64c4fe73dd5f 100644
> --- a/security/integrity/ima/ima_queue.c
> +++ b/security/integrity/ima/ima_queue.c
> @@ -371,6 +371,49 @@ int ima_queue_staged_delete_all(void)
>   	return 0;
>   }
>   
> +int ima_queue_delete_partial(unsigned long req_value)
> +{
> +	unsigned long req_value_copy = req_value;
> +	unsigned long size_to_remove = 0, num_to_remove = 0;
> +	LIST_HEAD(ima_measurements_trim);
> +	struct ima_queue_entry *qe;
> +	int ret = 0;
> +
> +	/*
> +	 * Safe to walk without rcu_read_lock(): single-writer
> +	 * exclusion in ima_fs.c prevents any concurrent modification
> +	 * to ima_measurements during this walk.
> +	 */
> +	list_for_each_entry_rcu(qe, &ima_measurements, later, true) {
> +		size_to_remove += get_binary_runtime_size(qe->entry);
> +		num_to_remove++;
> +
> +		if (--req_value_copy == 0)
> +			break;
> +	}
> +
> +	/* Not enough entries to delete. */
> +	if (req_value_copy > 0)
> +		return -ENOENT;
> +
> +	mutex_lock(&ima_extend_list_mutex);
> +	/*
> +	 * qe remains valid because ima_fs.c enforces single-writer exclusion.
> +	 */
> +	__list_cut_position(&ima_measurements_trim, &ima_measurements,
> +			    &qe->later);
> +
> +	atomic_long_sub(num_to_remove, &ima_num_entries[BINARY]);
> +
> +	if (IS_ENABLED(CONFIG_IMA_KEXEC))
> +		binary_runtime_size[BINARY] -= size_to_remove;
> +
> +	mutex_unlock(&ima_extend_list_mutex);
> +
> +	ima_queue_delete(&ima_measurements_trim, false);
> +	return ret;
> +}
> +
>   static void ima_queue_delete(struct list_head *head, bool flush_htable)
>   {
>   	struct ima_queue_entry *qe, *qe_tmp;