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FAILED: patch "[PATCH] ksmbd: Compare MACs in constant time" failed to apply to 6.12-stable tree

PATCH [email protected] 1 participant 1 message Mar 9

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Stable branch Kernel SMB3 server (ksmbd)
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The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x c5794709bc9105935dbedef8b9cf9c06f2b559fa
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026030936-unenvied-uneatable-3f0d@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From c5794709bc9105935dbedef8b9cf9c06f2b559fa Mon Sep 17 00:00:00 2001
From: Eric Biggers <[email protected]>
Date: Tue, 17 Feb 2026 20:28:29 -0800
Subject: [PATCH] ksmbd: Compare MACs in constant time

To prevent timing attacks, MAC comparisons need to be constant-time. Replace the memcmp() with the correct function, crypto_memneq().

Fixes e2f34481b24d ("cifsd: add server-side procedures for SMB3")
Cc [email protected]
Signed-off-by Eric Biggers <[email protected]>
Acked-by Namjae Jeon <[email protected]>
Signed-off-by Steve French <[email protected]>
fs/smb/server/Kconfig +1 -0
index 2775162c535c..12594879cb64 100644
@@ -13,6 +13,7 @@ config SMB_SERVER
 	select CRYPTO_LIB_MD5
 	select CRYPTO_LIB_SHA256
 	select CRYPTO_LIB_SHA512
+	select CRYPTO_LIB_UTILS
 	select CRYPTO_CMAC
 	select CRYPTO_AEAD2
 	select CRYPTO_CCM
fs/smb/server/auth.c +3 -1
index 580c4d303dc3..5fe8c667c6b1 100644
@@ -15,6 +15,7 @@
 #include <crypto/aead.h>
 #include <crypto/md5.h>
 #include <crypto/sha2.h>
+#include <crypto/utils.h>
 #include <linux/random.h>
 #include <linux/scatterlist.h>
 

@@ -165,7 +166,8 @@ int ksmbd_auth_ntlmv2(struct ksmbd_conn *conn, struct ksmbd_session *sess,
 			     ntlmv2_rsp, CIFS_HMAC_MD5_HASH_SIZE,
 			     sess->sess_key);
 
-	if (memcmp(ntlmv2->ntlmv2_hash, ntlmv2_rsp, CIFS_HMAC_MD5_HASH_SIZE) != 0)
+	if (crypto_memneq(ntlmv2->ntlmv2_hash, ntlmv2_rsp,
+			  CIFS_HMAC_MD5_HASH_SIZE))
 		return -EINVAL;
 	return 0;
 }
fs/smb/server/smb2pdu.c +3 -2
index 95901a78951c..743c629fe7ec 100644
@@ -4,6 +4,7 @@
  *   Copyright (C) 2018 Samsung Electronics Co., Ltd.
  */
 
+#include <crypto/utils.h>
 #include <linux/inetdevice.h>
 #include <net/addrconf.h>
 #include <linux/syscalls.h>

@@ -8880,7 +8881,7 @@ int smb2_check_sign_req(struct ksmbd_work *work)
 	ksmbd_sign_smb2_pdu(work->conn, work->sess->sess_key, iov, 1,
 			    signature);
 
-	if (memcmp(signature, signature_req, SMB2_SIGNATURE_SIZE)) {
+	if (crypto_memneq(signature, signature_req, SMB2_SIGNATURE_SIZE)) {
 		pr_err("bad smb2 signature\n");
 		return 0;
 	}

@@ -8968,7 +8969,7 @@ int smb3_check_sign_req(struct ksmbd_work *work)
 	if (ksmbd_sign_smb3_pdu(conn, signing_key, iov, 1, signature))
 		return 0;
 
-	if (memcmp(signature, signature_req, SMB2_SIGNATURE_SIZE)) {
+	if (crypto_memneq(signature, signature_req, SMB2_SIGNATURE_SIZE)) {
 		pr_err("bad smb2 signature\n");
 		return 0;
 	}