[PATCH][CIFS] Clarify SMB1 code for POSIX Lock

[Steve French <smfrench@xxxxxxxxx>]

Another trivial (Coverity reported issue) patch ...

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")
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
---
 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) {


-- 
Thanks,

Steve

From 7b7a11a7b5a865390621d156bd169a0a22dbeaf9 Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@xxxxxxxxxxxxx>
Date: Wed, 7 Jul 2021 14:03:54 -0500
Subject: [PATCH] CIFS: Clarify SMB1 code for POSIX Lock

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")
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
---
 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) {
-- 
2.30.2