From caeb105c15ea2431fa8da7ecfa242d0c68272426 Mon Sep 17 00:00:00 2001 From: Lincoln Wallace Date: Mon, 3 Aug 2026 10:50:21 -0300 Subject: [PATCH] ima: fix out-of-bounds read in xattr_verify() commit 5ff232d31106f45ac87c3b64e1d35a0667777797 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- 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 08b49bd1e8ca..9c972165d2b3 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -254,8 +254,13 @@ static int xattr_verify(enum ima_hooks func, struct integrity_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