[PATCH v6 8/8] ima: add FIRMWARE_PARTIAL_READ support

Scott Branden
2020-06-05T23:00:49Z

Add FIRMWARE_PARTIAL_READ support for integrity
measurement on partial reads of firmware files.

Signed-off-by: Scott Branden <scott.branden@broadcom.com>
---
drivers/base/firmware_loader/main.c | 6 +++++-
fs/exec.c | 6 ++++--
include/linux/fs.h | 1 +
security/integrity/ima/ima_main.c | 24 +++++++++++++++++++++++-
4 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
index 93e7fee42cd4..d0c42194af17 100644
--- a/drivers/base/firmware_loader/main.c
+++ b/drivers/base/firmware_loader/main.c
@@ -483,7 +483,11 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
/* Already populated data member means we're loading into a buffer */
if (!decompress && fw_priv->data) {
buffer = fw_priv->data;
- id = READING_FIRMWARE_PREALLOC_BUFFER;
+ if (fw_priv->opt == KERNEL_PREAD_PART)
+ id = READING_FIRMWARE_PARTIAL_READ;
+ else
+ id = READING_FIRMWARE_PREALLOC_BUFFER;
+
msize = fw_priv->allocated_size;
}

diff --git a/fs/exec.c b/fs/exec.c
index e5c241c07b75..3fbc2fee909f 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -968,7 +968,8 @@ int kernel_pread_file(struct file *file, void **buf, loff_t *size,
goto out;
}

- if (id != READING_FIRMWARE_PREALLOC_BUFFER)
+ if ((id != READING_FIRMWARE_PARTIAL_READ) &&
+ (id != READING_FIRMWARE_PREALLOC_BUFFER))
*buf = vmalloc(alloc_size);
if (!*buf) {
ret = -ENOMEM;
@@ -1000,7 +1001,8 @@ int kernel_pread_file(struct file *file, void **buf, loff_t *size,

out_free:
if (ret < 0) {
- if (id != READING_FIRMWARE_PREALLOC_BUFFER) {
+ if ((id != READING_FIRMWARE_PARTIAL_READ) &&
+ (id != READING_FIRMWARE_PREALLOC_BUFFER)) {
vfree(*buf);
*buf = NULL;
}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 76d463e4a628..3affcaa7c7b2 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3020,6 +3020,7 @@ extern int do_pipe_flags(int *, int);
#define __kernel_read_file_id(id) \
id(UNKNOWN, unknown) \
id(FIRMWARE, firmware) \
+ id(FIRMWARE_PARTIAL_READ, firmware) \
id(FIRMWARE_PREALLOC_BUFFER, firmware) \
id(FIRMWARE_EFI_EMBEDDED, firmware) \
id(MODULE, kernel-module) \
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 800fb3bba418..982debd59cc4 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -609,6 +609,9 @@ void ima_post_path_mknod(struct dentry *dentry)
*/
int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
{
+ enum ima_hooks func;
+ u32 secid;
+
/*
* READING_FIRMWARE_PREALLOC_BUFFER
*
@@ -617,11 +620,27 @@ int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
* of IMA's signature verification any more than when using two
* buffers?
*/
- return 0;
+ if (read_id != READING_FIRMWARE_PARTIAL_READ)
+ return 0;
+
+ if (!file) {
+ if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
+ (ima_appraise & IMA_APPRAISE_ENFORCE)) {
+ pr_err("Prevent firmware loading_store.\n");
+ return -EACCES; /* INTEGRITY_UNKNOWN */
+ }
+ return 0;
+ }
+
+ func = read_idmap[read_id] ?: FILE_CHECK;
+ security_task_getsecid(current, &secid);
+ return process_measurement(file, current_cred(), secid, NULL,
+ 0, MAY_READ, func);
}

const int read_idmap[READING_MAX_ID] = {
[READING_FIRMWARE] = FIRMWARE_CHECK,
+ [READING_FIRMWARE_PARTIAL_READ] = FIRMWARE_CHECK,
[READING_FIRMWARE_PREALLOC_BUFFER] = FIRMWARE_CHECK,
[READING_MODULE] = MODULE_CHECK,
[READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK,
@@ -648,6 +667,9 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
enum ima_hooks func;
u32 secid;

+ if (!file && read_id == READING_FIRMWARE_PARTIAL_READ)
+ return 0;
+
if (!file && read_id == READING_FIRMWARE) {
if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
(ima_appraise & IMA_APPRAISE_ENFORCE)) {
--
2.17.1