From 5ff232d31106f45ac87c3b64e1d35a0667777797 Mon Sep 17 00:00:00 2001 From: Lincoln Wallace Date: Mon, 3 Aug 2026 10:50:21 -0300 Subject: [PATCH 1/2] ima: fix out-of-bounds read in xattr_verify() The digest-length check in xattr_verify() mixes int and size_t: if (xattr_len - sizeof(xattr_value->type) - hash_start >= iint->ima_hash->length) sizeof() yields size_t, so the usual arithmetic conversions promote the whole left-hand side to unsigned 64-bit before the subtraction runs. For a truncated xattr this underflows instead of going negative: a 1-byte IMA_XATTR_DIGEST_NG xattr (xattr_len == 1, hash_start == 1) turns "1 - 1 - 1" into SIZE_MAX, which is trivially >= ima_hash->length. The check then passes and the following memcmp() reads iint->ima_hash->length bytes starting past the end of the buffer vfs_getxattr_alloc() allocated for it. Nothing upstream clamps xattr_len back into a safe range first: ima_get_hash_algo() only special-cases xattr_len < 2 to pick a default algorithm, and evm_verifyxattr() returns INTEGRITY_UNKNOWN rather than failing when no HMAC key is loaded, so a truncated security.ima value reaches the length check as-is. Rewrite the comparison so every operand stays a signed int and no implicit conversion to size_t can occur. Fixes: 3ea7a56067e6 ("ima: provide hash algo info in the xattr") Cc: stable@vger.kernel.org Signed-off-by: Lincoln Wallace Signed-off-by: Mimi Zohar --- security/integrity/ima/ima_appraise.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index 18d0d9154317..ced2e131b061 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -274,8 +274,13 @@ static int xattr_verify(enum ima_hooks func, struct ima_iint_cache *iint, } else { set_bit(IMA_DIGSIG, &iint->atomic_flags); } - if (xattr_len - sizeof(xattr_value->type) - hash_start >= - iint->ima_hash->length) + /* + * Use addition, not subtraction: sizeof() forces unsigned + * math and a short xattr_len would wrap around, bypassing + * this bounds check. + */ + if (xattr_len >= (int)sizeof(xattr_value->type) + hash_start + + (int)iint->ima_hash->length) /* * xattr length may be longer. md5 hash in previous * version occupied 20 bytes in xattr, instead of 16 From b80bed5c871a80151351342c065579405ce77145 Mon Sep 17 00:00:00 2001 From: Mimi Zohar Date: Mon, 27 Jul 2026 20:39:41 -0400 Subject: [PATCH 2/2] ima: Instantiate file_truncate and path_truncate hooks Instantiate the file_truncate and path_truncate LSM hooks to reset the action cache flags (IMA_DONE_MASK) as soon as truncation is requested, so the file, based on policy, is re-collected, re-measured, re-audited, and re-appraised on next access. Tested-by: Frederick Lawler Cc: stable@vger.kernel.org Signed-off-by: Mimi Zohar --- security/integrity/ima/ima_main.c | 39 +++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+) diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index 5cea53fc36df..ff52becc3031 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -687,6 +687,43 @@ static int ima_file_check(struct file *file, int mask) MAY_APPEND), FILE_CHECK, 0, false); } +/* + * ima_reset_action_flags - invalidate action flags after a content change + * @inode: inode of the file whose content is about to be truncated + * + * Clear IMA_DONE_MASK so the file is re-collected, re-measured, + * re-audited, and re-appraised on next access. + */ +static void ima_reset_action_flags(struct inode *inode) +{ + struct ima_iint_cache *iint; + + if (!ima_policy_flag || !S_ISREG(inode->i_mode)) + return; + + iint = ima_iint_find(inode); + if (!iint) + return; + + mutex_lock(&iint->mutex); + iint->flags &= ~IMA_DONE_MASK; + iint->measured_pcrs = 0; + mutex_unlock(&iint->mutex); + return; +} + +static int ima_path_truncate(const struct path *path) +{ + ima_reset_action_flags(path->dentry->d_inode); + return 0; +} + +static int ima_file_truncate(struct file *file) +{ + ima_reset_action_flags(file_inode(file)); + return 0; +} + static int __ima_inode_hash(struct inode *inode, struct file *file, char *buf, size_t buf_size) { @@ -1300,11 +1337,13 @@ static struct security_hook_list ima_hooks[] __ro_after_init = { LSM_HOOK_INIT(file_release, ima_file_free), LSM_HOOK_INIT(mmap_file, ima_file_mmap), LSM_HOOK_INIT(file_mprotect, ima_file_mprotect), + LSM_HOOK_INIT(file_truncate, ima_file_truncate), LSM_HOOK_INIT(kernel_load_data, ima_load_data), LSM_HOOK_INIT(kernel_post_load_data, ima_post_load_data), LSM_HOOK_INIT(kernel_read_file, ima_read_file), LSM_HOOK_INIT(kernel_post_read_file, ima_post_read_file), LSM_HOOK_INIT(path_post_mknod, ima_post_path_mknod), + LSM_HOOK_INIT(path_truncate, ima_path_truncate), #ifdef CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS LSM_HOOK_INIT(key_post_create_or_update, ima_post_key_create_or_update), #endif