FAILED: patch "[PATCH] smb: client: bound POSIX lock data area by response length" failed to apply to 6.1-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.1-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 <stable@vger.kernel.org>.

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-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 8fc9af68c57156ff64769f30e831553cd03b3000
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026110407-custody-treadmill-c8a2@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From 8fc9af68c57156ff64769f30e831553cd03b3000 Mon Sep 17 00:00:00 2001
From: Ratnaker Gautam <ratnaker.gautam@kuleuven.be>
Date: Sun, 18 Oct 2026 00:49:33 +0200
Subject: [PATCH] smb: client: bound POSIX lock data area by response length

CIFSSMBPosixLock() receives a TRANS2 response whose server-provided
DataOffset and DataCount are not required by validate_t2() to describe an
interval inside the response. A server can therefore make the client read a
cifs_posix_lock beyond the response buffer and return those kernel bytes
through F_GETLK.

Use smbCalcSize() to obtain the full response length after any multipart
TRANS2 reassembly, then reject data areas that extend past it before
dereferencing them.

Fixes: fc94cdb94462 ("[CIFS] Fix new POSIX Locking for setting lock_type correctly on unlock")
Reported-by: Ratnaker Gautam <ratnaker.gautam@kuleuven.be>
Cc: stable@vger.kernel.org
Signed-off-by: Ratnaker Gautam <ratnaker.gautam@kuleuven.be>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>

diff --git a/fs/smb/client/cifssmb.c b/fs/smb/client/cifssmb.c
index 50ca062a22bf..e335686a68f2 100644
--- a/fs/smb/client/cifssmb.c
+++ b/fs/smb/client/cifssmb.c
@@ -2369,6 +2369,7 @@ CIFSSMBPosixLock(const unsigned int xid, struct cifs_tcon *tcon,
 		cifs_dbg(FYI, "Send error in Posix Lock = %d\n", rc);
 	} else if (pLockData) {
 		/* lock structure can be returned on get */
+		unsigned int rsp_len;
 		__u16 data_offset;
 		__u16 data_count;
 		rc = validate_t2((struct smb_t2_rsp *)pSMBr);
@@ -2380,11 +2381,18 @@ CIFSSMBPosixLock(const unsigned int xid, struct cifs_tcon *tcon,
 		}
 		data_offset = le16_to_cpu(pSMBr->t2.DataOffset);
 		data_count  = le16_to_cpu(pSMBr->t2.DataCount);
+		rsp_len = smbCalcSize(&pSMBr->hdr);
 		if (data_count < sizeof(struct cifs_posix_lock)) {
 			rc = smb_EIO2(smb_eio_trace_lock_data_too_small,
 				      data_count, sizeof(struct cifs_posix_lock));
 			goto plk_err_exit;
 		}
+		if (data_offset > rsp_len ||
+		    data_count > rsp_len - data_offset) {
+			rc = smb_EIO2(smb_eio_trace_lock_data_area,
+				      data_offset, data_count);
+			goto plk_err_exit;
+		}
 		parm_data = (struct cifs_posix_lock *)
 			((char *)&pSMBr->hdr.Protocol + data_offset);
 		if (parm_data->lock_type == cpu_to_le16(CIFS_UNLCK))
diff --git a/fs/smb/client/trace.h b/fs/smb/client/trace.h
index 2708bedb49ab..5331ce6dc8b3 100644
--- a/fs/smb/client/trace.h
+++ b/fs/smb/client/trace.h
@@ -44,6 +44,7 @@
 	EM(smb_eio_trace_ioctl_no_rsp,			"ioctl_no_rsp") \
 	EM(smb_eio_trace_ioctl_out_off,			"ioctl_out_off") \
 	EM(smb_eio_trace_lock_bcc_too_small,		"lock_bcc_too_small") \
+	EM(smb_eio_trace_lock_data_area,		"lock_data_area") \
 	EM(smb_eio_trace_lock_data_too_small,		"lock_data_too_small") \
 	EM(smb_eio_trace_malformed_ksid_key,		"malformed_ksid_key") \
 	EM(smb_eio_trace_malformed_sid_key,		"malformed_sid_key") \