CVE-2026-74671ima: fix out-of-bounds read in xattr_verify()

Official description

In the Linux kernel, the following vulnerability has been resolved: 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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/d823b5f4557083d1dd92096f796a78a2b1b06d10
• https://git.kernel.org/stable/c/caeb105c15ea2431fa8da7ecfa242d0c68272426
• https://git.kernel.org/stable/c/a784b4732ac7e51862b9b210c2d8b2ab9e83568c
• https://git.kernel.org/stable/c/b6cb134707a2127d90a58d69dd818679cae8033c
• https://git.kernel.org/stable/c/7e515b6c9aab452a4f0734bd7208e4e780e164ca
• https://git.kernel.org/stable/c/27f3924061592d0ef6b04e16f48754b6cb6adf27
• https://git.kernel.org/stable/c/dd04114af0d451091f7b8cbd26d9e37d011e9131
• https://git.kernel.org/stable/c/5ff232d31106f45ac87c3b64e1d35a0667777797