FAILED: patch "[PATCH] smb: client: fix UAF and buffer leak in cifs_check_trans2()" failed to apply to 6.6-stable tree

PATCH New [email protected] 2 participants 5 messages Sep 3 – Sep 7

Subsystems (5)

Stable branch VFS SMB client (CIFS) Kernel SMB3 server (ksmbd) +1 more subsystems

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lore

[email protected]

author maintainer

2026-09-03 13:48 UTC #0 lore raw

The patch below does not apply to the 6.6-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-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 730d0bb19507b9e19c2fe5343109ac618e2fbce5
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090303-fiddling-giant-6389@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

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

From 730d0bb19507b9e19c2fe5343109ac618e2fbce5 Mon Sep 17 00:00:00 2001
From: Frank Sorenson <[email protected]>
Date: Wed, 12 Aug 2026 21:39:51 -0500
Subject: [PATCH] smb: client: fix UAF and buffer leak in cifs_check_trans2()
for malformed secondary T2

When a valid primary TRANSACT2 response has been received (mid->resp_buf set, mid->multiRsp true) and a subsequent secondary response causes cifs_check_trans2() to return false -- either because the SMB header is invalid (malformed != 0) or because check2ndT2() rejects the PDU -- handle_mid() overwrites mid->resp_buf with the new buffer (leaking the primary buffer) and, because mid->multiRsp is set, skips the server->smallbuf/bigbuf NULL-out. When the user thread frees mid->resp_buf, server->smallbuf or server->bigbuf is left dangling; the demux thread reuses it for the next packet, resulting in a use-after-free.

Combine both early-exit conditions and, when mid->multiRsp is already set, abort the pending transaction inline: set multiEnd, call dequeue_mid() with malformed=true, and return true so handle_mid() exits without touching mid->resp_buf or the server buffer pointers.

Fixes 316cf94a910f ("CIFS: Move trans2 processing to ops struct")

Cc [email protected] # cifs_check_trans2() is in smb1ops.c on kernels < 7.0

Signed-off-by Frank Sorenson <[email protected]>

Signed-off-by Namjae Jeon <[email protected]>

Signed-off-by Paulo Alcantara <[email protected]>

fs/smb/client/smb1transport.c +11 -3

index 66daa5a37e4a..42e95cc1bd89 100644
@@ -449,10 +449,18 @@ bool
 cifs_check_trans2(struct mid_q_entry *mid, struct TCP_Server_Info *server,
 		  char *buf, int malformed)
 {
-	if (malformed)
-		return false;
-	if (check2ndT2(buf) <= 0)
+	if (malformed || check2ndT2(buf) <= 0) {
+		/* mid->multiRsp blocks the server buf detach in handle_mid();
+		 * returning false here would leak resp_buf and leave a dangling
+		 * server->smallbuf/bigbuf after the user thread frees resp_buf.
+		 */
+		if (mid->multiRsp) {
+			mid->multiEnd = true;
+			dequeue_mid(server, mid, true);
+			return true;
+		}
 		return false;
+	}
 	mid->multiRsp = true;
 	if (mid->resp_buf) {
 		/* merge response - fix up 1st*/

Sasha Levin

maintainer

2026-09-07 20:00 UTC #1 lore raw

PATCH 1/4 cifs: Remove the server pointer from smb_message

From: David Howells <[email protected]>

[ Upstream commit 87fba18abbb8433a47045c785f2edc027e4d2bc5 ]

Remove the server pointer from smb_message and instead pass it down to all the things that access it.

Signed-off-by David Howells <[email protected]>

Reviewed-by Paulo Alcantara (Red Hat) <[email protected]>

cc Shyam Prasad N <[email protected]>

cc Tom Talpey <[email protected]> (RDMA, smbdirect)

cc [email protected]

Signed-off-by Steve French <[email protected]>

[ sashal: Reduced backport -- upstream 87fba18abbb84 touches 12 file(s), this
backport carries 6. Not backported here:
fs/smb/client/cifsfs.c
fs/smb/client/cifsglob.h
fs/smb/client/cifssmb.c
fs/smb/client/cifstransport.c
fs/smb/client/netmisc.c
fs/smb/client/smb1ops.c
fs/smb/client/smb2pdu.c
fs/smb/client/smb2transport.c
This note is generated from the file lists only; see the resolution record for the reasoning. ]

Stable-dep-of: 730d0bb19507 ("smb: client: fix UAF and buffer leak in cifs_check_trans2() for malformed secondary T2")

Signed-off-by Sasha Levin <[email protected]>

---
 fs/smb/client/Makefile                       |  2 +-
 fs/smb/client/cifsproto.h                    |  3 ++-
 fs/smb/client/connect.c                      | 11 ++++++-----
 fs/smb/client/{smb1ops.c => smb1transport.c} |  2 +-
 fs/smb/client/smb2ops.c                      | 14 +++++++-------
 fs/smb/client/transport.c                    |  4 ++--
 6 files changed, 19 insertions(+), 17 deletions(-)
 rename fs/smb/client/{smb1ops.c => smb1transport.c} (99%)

fs/smb/client/Makefile +1 -1

index e11985f2460b2..3c2af1fa9fa24 100644
@@ -32,4 +32,4 @@ cifs-$(CONFIG_CIFS_SMB_DIRECT) += smbdirect.o
 
 cifs-$(CONFIG_CIFS_ROOT) += cifsroot.o
 
-cifs-$(CONFIG_CIFS_ALLOW_INSECURE_LEGACY) += smb1ops.o cifssmb.o
+cifs-$(CONFIG_CIFS_ALLOW_INSECURE_LEGACY) += smb1transport.o cifssmb.o

fs/smb/client/cifsproto.h +2 -1

index 1f37bc2923fb8..36f5010d3787d 100644
@@ -253,7 +253,8 @@ extern unsigned int setup_special_mode_ACE(struct smb_ace *pace,
 					   __u64 nmode);
 extern unsigned int setup_special_user_owner_ACE(struct smb_ace *pace);
 
-extern void dequeue_mid(struct mid_q_entry *mid, bool malformed);
+extern void dequeue_mid(struct TCP_Server_Info *server,
+			struct mid_q_entry *mid, bool malformed);
 extern int cifs_read_from_socket(struct TCP_Server_Info *server, char *buf,
 			         unsigned int to_read);
 extern ssize_t cifs_discard_from_socket(struct TCP_Server_Info *server,

fs/smb/client/connect.c +6 -5

index 68a000956d957..46a48e81a3847 100644
@@ -882,12 +882,13 @@ is_smb_response(struct TCP_Server_Info *server, unsigned char type)
 }
 
 void
-dequeue_mid(struct mid_q_entry *mid, bool malformed)
+dequeue_mid(struct TCP_Server_Info *server, struct mid_q_entry *mid,
+	    bool malformed)
 {
 #ifdef CONFIG_CIFS_STATS2
 	mid->when_received = jiffies;
 #endif
-	spin_lock(&mid->server->mid_lock);
+	spin_lock(&server->mid_lock);
 	if (!malformed)
 		mid->mid_state = MID_RESPONSE_RECEIVED;
 	else

@@ -897,12 +898,12 @@ dequeue_mid(struct mid_q_entry *mid, bool malformed)
 	 * function has finished processing it is a bug.
 	 */
 	if (mid->mid_flags & MID_DELETED) {
-		spin_unlock(&mid->server->mid_lock);
+		spin_unlock(&server->mid_lock);
 		pr_warn_once("trying to dequeue a deleted mid\n");
 	} else {
 		list_del_init(&mid->qhead);
 		mid->mid_flags |= MID_DELETED;
-		spin_unlock(&mid->server->mid_lock);
+		spin_unlock(&server->mid_lock);
 	}
 }

@@ -938,7 +939,7 @@ handle_mid(struct mid_q_entry *mid, struct TCP_Server_Info *server,
 		else
 			server->smallbuf = NULL;
 	}
-	dequeue_mid(mid, malformed);
+	dequeue_mid(server, mid, malformed);
 }
 
 int

fs/smb/client/smb1transport.c renamed from fs/smb/client/smb1ops.c +1 -1

similarity index 99%
rename from fs/smb/client/smb1ops.c
rename to fs/smb/client/smb1transport.c
index c80b291a14a57..824604cb0e468 100644
@@ -398,7 +398,7 @@ cifs_check_trans2(struct mid_q_entry *mid, struct TCP_Server_Info *server,
 			return true;
 		/* All parts received or packet is malformed. */
 		mid->multiEnd = true;
-		dequeue_mid(mid, malformed);
+		dequeue_mid(server, mid, malformed);
 		return true;
 	}
 	if (!server->large_buf) {

fs/smb/client/smb2ops.c +7 -7

index 8a15694c1bbb5..b86457fdc08a1 100644
@@ -4627,7 +4627,7 @@ handle_read_data(struct TCP_Server_Info *server, struct mid_q_entry *mid,
 		if (is_offloaded)
 			mid->mid_state = MID_RESPONSE_RECEIVED;
 		else
-			dequeue_mid(mid, false);
+			dequeue_mid(server, mid, false);
 		return 0;
 	}

@@ -4654,7 +4654,7 @@ handle_read_data(struct TCP_Server_Info *server, struct mid_q_entry *mid,
 		if (is_offloaded)
 			mid->mid_state = MID_RESPONSE_MALFORMED;
 		else
-			dequeue_mid(mid, rdata->result);
+			dequeue_mid(server, mid, rdata->result);
 		return 0;
 	}

@@ -4673,7 +4673,7 @@ handle_read_data(struct TCP_Server_Info *server, struct mid_q_entry *mid,
 			if (is_offloaded)
 				mid->mid_state = MID_RESPONSE_MALFORMED;
 			else
-				dequeue_mid(mid, rdata->result);
+				dequeue_mid(server, mid, rdata->result);
 			return 0;
 		}

@@ -4683,7 +4683,7 @@ handle_read_data(struct TCP_Server_Info *server, struct mid_q_entry *mid,
 			if (is_offloaded)
 				mid->mid_state = MID_RESPONSE_MALFORMED;
 			else
-				dequeue_mid(mid, rdata->result);
+				dequeue_mid(server, mid, rdata->result);
 			return 0;
 		}

@@ -4694,7 +4694,7 @@ handle_read_data(struct TCP_Server_Info *server, struct mid_q_entry *mid,
 			if (is_offloaded)
 				mid->mid_state = MID_RESPONSE_MALFORMED;
 			else
-				dequeue_mid(mid, rdata->result);
+				dequeue_mid(server, mid, rdata->result);
 			return 0;
 		}
 		rdata->got_bytes = pages_len;

@@ -4714,14 +4714,14 @@ handle_read_data(struct TCP_Server_Info *server, struct mid_q_entry *mid,
 		if (is_offloaded)
 			mid->mid_state = MID_RESPONSE_MALFORMED;
 		else
-			dequeue_mid(mid, rdata->result);
+			dequeue_mid(server, mid, rdata->result);
 		return 0;
 	}
 
 	if (is_offloaded)
 		mid->mid_state = MID_RESPONSE_RECEIVED;
 	else
-		dequeue_mid(mid, false);
+		dequeue_mid(server, mid, false);
 	return 0;
 }

fs/smb/client/transport.c +2 -2

index a47242a0f5c6d..6a1de5973ea05 100644
@@ -1690,7 +1690,7 @@ __cifs_readv_discard(struct TCP_Server_Info *server, struct mid_q_entry *mid,
 	int length;
 
 	length = cifs_discard_remaining_data(server);
-	dequeue_mid(mid, malformed);
+	dequeue_mid(server, mid, malformed);
 	mid->resp_buf = server->smallbuf;
 	server->smallbuf = NULL;
 	return length;

@@ -1833,7 +1833,7 @@ cifs_readv_receive(struct TCP_Server_Info *server, struct mid_q_entry *mid)
 	if (server->total_read < buflen)
 		return cifs_readv_discard(server, mid);
 
-	dequeue_mid(mid, false);
+	dequeue_mid(server, mid, false);
 	mid->resp_buf = server->smallbuf;
 	server->smallbuf = NULL;
 	return length;

Signature · 1 line

2.53.0

Sasha Levin

maintainer

2026-09-07 20:00 UTC #2 lore raw

PATCH 2/4 cifs: Scripted clean up fs/smb/client/fscache.h

From: David Howells <[email protected]>

[ Upstream commit bc3de356aae666de5d8b5131545be87cf7754431 ]

Remove externs, correct argument names and reformat declarations.

Signed-off-by David Howells <[email protected]>

cc Steve French <[email protected]>

cc Paulo Alcantara <[email protected]>

cc Enzo Matsumiya <[email protected]>

cc [email protected]

Acked-by Enzo Matsumiya <[email protected]>

Signed-off-by Steve French <[email protected]>

Stable-dep-of: 730d0bb19507 ("smb: client: fix UAF and buffer leak in cifs_check_trans2() for malformed secondary T2")

Signed-off-by Sasha Levin <[email protected]>

---
 fs/smb/client/fscache.h | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

fs/smb/client/fscache.h +5 -5

index 1f2ea9f5cc9a8..4c2e269a268ed 100644
@@ -38,12 +38,12 @@ struct cifs_fscache_inode_coherency_data {
 /*
  * fscache.c
  */
-extern int cifs_fscache_get_super_cookie(struct cifs_tcon *);
-extern void cifs_fscache_release_super_cookie(struct cifs_tcon *);
+int cifs_fscache_get_super_cookie(struct cifs_tcon *tcon);
+void cifs_fscache_release_super_cookie(struct cifs_tcon *tcon);
 
-extern void cifs_fscache_get_inode_cookie(struct inode *inode);
-extern void cifs_fscache_release_inode_cookie(struct inode *);
-extern void cifs_fscache_unuse_inode_cookie(struct inode *inode, bool update);
+void cifs_fscache_get_inode_cookie(struct inode *inode);
+void cifs_fscache_release_inode_cookie(struct inode *inode);
+void cifs_fscache_unuse_inode_cookie(struct inode *inode, bool update);
 
 static inline
 void cifs_fscache_fill_coherency(struct inode *inode,

Signature · 1 line

2.53.0

Sasha Levin

maintainer

2026-09-07 20:00 UTC #3 lore raw

PATCH 3/4 cifs: SMB1 split: Create smb1proto.h for SMB1 declarations

In reply to Sasha Levin

From: David Howells <[email protected]>

[ Upstream commit 86c666506ea2c42649879eeac7f29e7bedef2f23 ]

Signed-off-by David Howells <[email protected]>

cc Steve French <[email protected]>

cc Paulo Alcantara <[email protected]>

cc Enzo Matsumiya <[email protected]>

cc [email protected]

Acked-by Enzo Matsumiya <[email protected]>

Signed-off-by Steve French <[email protected]>

Stable-dep-of: 730d0bb19507 ("smb: client: fix UAF and buffer leak in cifs_check_trans2() for malformed secondary T2")

Signed-off-by Sasha Levin <[email protected]>

---
 fs/smb/client/cifsglob.h  |  2 --
 fs/smb/client/cifsproto.h | 11 +----------
 fs/smb/client/smb1proto.h | 38 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 39 insertions(+), 12 deletions(-)
 create mode 100644 fs/smb/client/smb1proto.h

fs/smb/client/cifsglob.h +0 -2

index a4e0618c58efc..6c4f31fec2141 100644
@@ -2098,8 +2098,6 @@ extern mempool_t *cifs_mid_poolp;
 
 /* Operations for different SMB versions */
 #ifdef CONFIG_CIFS_ALLOW_INSECURE_LEGACY
-extern struct smb_version_operations smb1_operations;
-extern struct smb_version_values smb1_values;
 extern struct smb_version_operations smb20_operations;
 extern struct smb_version_values smb20_values;
 #endif /* CIFS_ALLOW_INSECURE_LEGACY */

fs/smb/client/cifsproto.h +1 ~~-10~~

index 36f5010d3787d..9f0a6eaa9b4e3 100644
@@ -13,6 +13,7 @@
 #ifdef CONFIG_CIFS_DFS_UPCALL
 #include "dfs_cache.h"
 #endif
+#include "smb1proto.h"
 
 struct statfs;
 struct smb_rqst;

@@ -424,16 +425,6 @@ extern int CIFSSMBSetFileSize(const unsigned int xid, struct cifs_tcon *tcon,
 			      struct cifsFileInfo *cfile, __u64 size,
 			      bool set_allocation);
 
-struct cifs_unix_set_info_args {
-	__u64	ctime;
-	__u64	atime;
-	__u64	mtime;
-	__u64	mode;
-	kuid_t	uid;
-	kgid_t	gid;
-	dev_t	device;
-};
-
 extern int CIFSSMBUnixSetFileInfo(const unsigned int xid,
 				  struct cifs_tcon *tcon,
 				  const struct cifs_unix_set_info_args *args,

fs/smb/client/smb1proto.h new file +38 -0

new file mode 100644
index 0000000000000..a73213f6a2aa1
@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: LGPL-2.1 */
+/*
+ *
+ *   Copyright (c) International Business Machines  Corp., 2002,2008
+ *   Author(s): Steve French ([email protected])
+ *
+ */
+#ifndef _SMB1PROTO_H
+#define _SMB1PROTO_H
+
+struct cifs_unix_set_info_args {
+	__u64	ctime;
+	__u64	atime;
+	__u64	mtime;
+	__u64	mode;
+	kuid_t	uid;
+	kgid_t	gid;
+	dev_t	device;
+};
+
+#ifdef CONFIG_CIFS_ALLOW_INSECURE_LEGACY
+
+/*
+ * cifssmb.c
+ */
+
+/*
+ * smb1ops.c
+ */
+extern struct smb_version_operations smb1_operations;
+extern struct smb_version_values smb1_values;
+
+/*
+ * smb1transport.c
+ */
+
+#endif /* CONFIG_CIFS_ALLOW_INSECURE_LEGACY */
+#endif /* _SMB1PROTO_H */

Signature · 1 line

2.53.0

Sasha Levin

maintainer

2026-09-07 20:00 UTC #4 lore raw

PATCH 4/4 smb: client: fix UAF and buffer leak in cifs_check_trans2() for malformed secondary T2

In reply to Sasha Levin

From: Frank Sorenson <[email protected]>

[ Upstream commit 730d0bb19507b9e19c2fe5343109ac618e2fbce5 ]

Fixes 316cf94a910f ("CIFS: Move trans2 processing to ops struct")

Cc [email protected] # cifs_check_trans2() is in smb1ops.c on kernels < 7.0

Signed-off-by Frank Sorenson <[email protected]>

Signed-off-by Namjae Jeon <[email protected]>

Signed-off-by Paulo Alcantara <[email protected]>

Signed-off-by Sasha Levin <[email protected]>

---
 fs/smb/client/smb1transport.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

fs/smb/client/smb1transport.c +11 -3

index 824604cb0e468..de240840d59ff 100644
@@ -386,10 +386,18 @@ static bool
 cifs_check_trans2(struct mid_q_entry *mid, struct TCP_Server_Info *server,
 		  char *buf, int malformed)
 {
-	if (malformed)
-		return false;
-	if (check2ndT2(buf) <= 0)
+	if (malformed || check2ndT2(buf) <= 0) {
+		/* mid->multiRsp blocks the server buf detach in handle_mid();
+		 * returning false here would leak resp_buf and leave a dangling
+		 * server->smallbuf/bigbuf after the user thread frees resp_buf.
+		 */
+		if (mid->multiRsp) {
+			mid->multiEnd = true;
+			dequeue_mid(server, mid, true);
+			return true;
+		}
 		return false;
+	}
 	mid->multiRsp = true;
 	if (mid->resp_buf) {
 		/* merge response - fix up 1st*/

Signature · 1 line

2.53.0