From: Steve French <stfrench@microsoft.com>
Date: Wed, 7 Jul 2021 14:03:54 -0500
Subject: [PATCH] CIFS: Clarify SMB1 code for POSIX Lock
Git-commit: d4dc277c480c1faf87d452467d16f513b7ae2fb8
References: bsc#1190317
Patch-mainline: v5.14-rc1

Coverity also complains about the way we calculate the offset
(starting from the address of a 4 byte array within the
header structure rather than from the beginning of the struct
plus 4 bytes) for SMB1 PosixLock. This changeset
doesn't change the address but makes it slightly clearer.

Addresses-Coverity: 711520 ("Out of bounds write")
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>
Acked-by: Enzo Matsumiya <ematsumiya@suse.de>
---
 fs/cifs/cifssmb.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 16bd4cf3bceb..f72e3b3dca69 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -2537,8 +2537,9 @@ CIFSSMBPosixLock(const unsigned int xid, struct cifs_tcon *tcon,
 	pSMB->TotalDataCount = pSMB->DataCount;
 	pSMB->TotalParameterCount = pSMB->ParameterCount;
 	pSMB->ParameterOffset = cpu_to_le16(param_offset);
+	/* SMB offsets are from the beginning of SMB which is 4 bytes in, after RFC1001 field */
 	parm_data = (struct cifs_posix_lock *)
-			(((char *) &pSMB->hdr.Protocol) + offset);
+			(((char *)pSMB) + offset + 4);
 
 	parm_data->lock_type = cpu_to_le16(lock_type);
 	if (waitFlag) {
-- 
2.33.0