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authorMimi Zohar <zohar@linux.ibm.com>2023-10-18 14:47:02 -0400
committerMimi Zohar <zohar@linux.ibm.com>2023-10-31 08:22:36 -0400
commitb836c4d29f2744200b2af41e14bf50758dddc818 (patch)
tree4ec0534db76707ad1e7d5a0ffe3a1bcd5b140901 /security/integrity
parentb46503068cb9ed63ff1d8250f143354ead0b16eb (diff)
ima: detect changes to the backing overlay file
Commit 18b44bc5a672 ("ovl: Always reevaluate the file signature for IMA") forced signature re-evaulation on every file access. Instead of always re-evaluating the file's integrity, detect a change to the backing file, by comparing the cached file metadata with the backing file's metadata. Verifying just the i_version has not changed is insufficient. In addition save and compare the i_ino and s_dev as well. Reviewed-by: Amir Goldstein <amir73il@gmail.com> Tested-by: Eric Snowberg <eric.snowberg@oracle.com> Tested-by: Raul E Rangel <rrangel@chromium.org> Cc: stable@vger.kernel.org Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Diffstat (limited to 'security/integrity')
-rw-r--r--security/integrity/ima/ima_api.c5
-rw-r--r--security/integrity/ima/ima_main.c16
-rw-r--r--security/integrity/integrity.h2
3 files changed, 22 insertions, 1 deletions
diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index 452e80b541e5..597ea0c4d72f 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -243,6 +243,7 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
{
const char *audit_cause = "failed";
struct inode *inode = file_inode(file);
+ struct inode *real_inode = d_real_inode(file_dentry(file));
const char *filename = file->f_path.dentry->d_name.name;
struct ima_max_digest_data hash;
struct kstat stat;
@@ -302,6 +303,10 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
iint->ima_hash = tmpbuf;
memcpy(iint->ima_hash, &hash, length);
iint->version = i_version;
+ if (real_inode != inode) {
+ iint->real_ino = real_inode->i_ino;
+ iint->real_dev = real_inode->i_sb->s_dev;
+ }
/* Possibly temporary failure due to type of read (eg. O_DIRECT) */
if (!result)
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 365db0e43d7c..cc1217ac2c6f 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -25,6 +25,7 @@
#include <linux/xattr.h>
#include <linux/ima.h>
#include <linux/fs.h>
+#include <linux/iversion.h>
#include "ima.h"
@@ -207,7 +208,7 @@ static int process_measurement(struct file *file, const struct cred *cred,
u32 secid, char *buf, loff_t size, int mask,
enum ima_hooks func)
{
- struct inode *inode = file_inode(file);
+ struct inode *backing_inode, *inode = file_inode(file);
struct integrity_iint_cache *iint = NULL;
struct ima_template_desc *template_desc = NULL;
char *pathbuf = NULL;
@@ -284,6 +285,19 @@ static int process_measurement(struct file *file, const struct cred *cred,
iint->measured_pcrs = 0;
}
+ /* Detect and re-evaluate changes made to the backing file. */
+ backing_inode = d_real_inode(file_dentry(file));
+ if (backing_inode != inode &&
+ (action & IMA_DO_MASK) && (iint->flags & IMA_DONE_MASK)) {
+ if (!IS_I_VERSION(backing_inode) ||
+ backing_inode->i_sb->s_dev != iint->real_dev ||
+ backing_inode->i_ino != iint->real_ino ||
+ !inode_eq_iversion(backing_inode, iint->version)) {
+ iint->flags &= ~IMA_DONE_MASK;
+ iint->measured_pcrs = 0;
+ }
+ }
+
/* Determine if already appraised/measured based on bitmask
* (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
* IMA_AUDIT, IMA_AUDITED)
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index d7553c93f5c0..9561db7cf6b4 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -164,6 +164,8 @@ struct integrity_iint_cache {
unsigned long flags;
unsigned long measured_pcrs;
unsigned long atomic_flags;
+ unsigned long real_ino;
+ dev_t real_dev;
enum integrity_status ima_file_status:4;
enum integrity_status ima_mmap_status:4;
enum integrity_status ima_bprm_status:4;