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 6.18] smb: client: Compare MACs in constant time
Date: Tue, 10 Mar 2026 12:50:20 -0700 [thread overview]
Message-ID: <20260310195020.70563-1-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 801824825ecf2..b9e20bcaa8b5c 100644
--- a/fs/smb/client/cifsencrypt.c
+++ b/fs/smb/client/cifsencrypt.c
@@ -24,10 +24,11 @@
#include <linux/iov_iter.h>
#include <crypto/aead.h>
#include <crypto/arc4.h>
#include <crypto/md5.h>
#include <crypto/sha2.h>
+#include <crypto/utils.h>
static int cifs_sig_update(struct cifs_calc_sig_ctx *ctx,
const u8 *data, size_t len)
{
if (ctx->md5) {
@@ -275,11 +276,11 @@ 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 6a9b80385b86b..211305d43f8d4 100644
--- a/fs/smb/client/smb2transport.c
+++ b/fs/smb/client/smb2transport.c
@@ -18,10 +18,11 @@
#include <asm/processor.h>
#include <linux/mempool.h>
#include <linux/highmem.h>
#include <crypto/aead.h>
#include <crypto/sha2.h>
+#include <crypto/utils.h>
#include "cifsglob.h"
#include "cifsproto.h"
#include "smb2proto.h"
#include "cifs_debug.h"
#include "../common/smb2status.h"
@@ -615,11 +616,12 @@ smb2_verify_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
rc = smb3_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: 6258e292d7463f96d0f06dff2a39093a54c9d16f
--
2.53.0
reply other threads:[~2026-03-10 19:50 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260310195020.70563-1-ebiggers@kernel.org \
--to=ebiggers@kernel.org \
--cc=linux-cifs@vger.kernel.org \
--cc=linux-crypto@vger.kernel.org \
--cc=pc@manguebit.org \
--cc=stable@vger.kernel.org \
--cc=stfrench@microsoft.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox