From: Eric Biggers <ebiggers@kernel.org>
To: stable@vger.kernel.org
Cc: linux-crypto@vger.kernel.org, linux-cifs@vger.kernel.org,
Eric Biggers <ebiggers@kernel.org>,
"Paulo Alcantara (Red Hat)" <pc@manguebit.org>,
Steve French <stfrench@microsoft.com>
Subject: [PATCH 6.6] smb: client: Compare MACs in constant time
Date: Tue, 10 Mar 2026 12:50:58 -0700 [thread overview]
Message-ID: <20260310195058.70682-1-ebiggers@kernel.org> (raw)
commit 26bc83b88bbbf054f0980a4a42047a8d1e210e4c upstream.
To prevent timing attacks, MAC comparisons need to be constant-time.
Replace the memcmp() with the correct function, crypto_memneq().
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Acked-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
---
fs/smb/client/cifsencrypt.c | 3 ++-
fs/smb/client/smb2transport.c | 4 +++-
2 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/fs/smb/client/cifsencrypt.c b/fs/smb/client/cifsencrypt.c
index da3d003cb43db..3d6b663212335 100644
--- a/fs/smb/client/cifsencrypt.c
+++ b/fs/smb/client/cifsencrypt.c
@@ -21,10 +21,11 @@
#include <linux/random.h>
#include <linux/highmem.h>
#include <linux/fips.h>
#include "../common/arc4.h"
#include <crypto/aead.h>
+#include <crypto/utils.h>
/*
* Hash data from a BVEC-type iterator.
*/
static int cifs_shash_bvec(const struct iov_iter *iter, ssize_t maxsize,
@@ -369,11 +370,11 @@ int cifs_verify_signature(struct smb_rqst *rqst,
return rc;
/* cifs_dump_mem("what we think it should be: ",
what_we_think_sig_should_be, 16); */
- if (memcmp(server_response_sig, what_we_think_sig_should_be, 8))
+ if (crypto_memneq(server_response_sig, what_we_think_sig_should_be, 8))
return -EACCES;
else
return 0;
}
diff --git a/fs/smb/client/smb2transport.c b/fs/smb/client/smb2transport.c
index 99081e9d6283a..daf8ba2cd8a10 100644
--- a/fs/smb/client/smb2transport.c
+++ b/fs/smb/client/smb2transport.c
@@ -17,10 +17,11 @@
#include <linux/uaccess.h>
#include <asm/processor.h>
#include <linux/mempool.h>
#include <linux/highmem.h>
#include <crypto/aead.h>
+#include <crypto/utils.h>
#include "cifsglob.h"
#include "cifsproto.h"
#include "smb2proto.h"
#include "cifs_debug.h"
#include "smb2status.h"
@@ -730,11 +731,12 @@ smb2_verify_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
rc = server->ops->calc_signature(rqst, server, true);
if (rc)
return rc;
- if (memcmp(server_response_sig, shdr->Signature, SMB2_SIGNATURE_SIZE)) {
+ if (crypto_memneq(server_response_sig, shdr->Signature,
+ SMB2_SIGNATURE_SIZE)) {
cifs_dbg(VFS, "sign fail cmd 0x%x message id 0x%llx\n",
shdr->Command, shdr->MessageId);
return -EACCES;
} else
return 0;
base-commit: 4fc00fe35d46b4fc8dac2eb543a0e3d44bb15f47
--
2.53.0
reply other threads:[~2026-03-10 19:51 UTC|newest]
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