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

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

[Steve French]

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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 CIFSPOSIXCreate. This changeset
doesn't change the address but makes it slightly clearer.

Addresses-Coverity: 711518 ("Out of bounds write")
Signed-off-by: Steve French <stfrench@microsoft.com>
---
 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 f72e3b3dca69..d4144c182604 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -1081,7 +1081,8 @@ CIFSPOSIXCreate(const unsigned int xid, struct
cifs_tcon *tcon,
  param_offset = offsetof(struct smb_com_transaction2_spi_req,
  InformationLevel) - 4;
  offset = param_offset + params;
- pdata = (OPEN_PSX_REQ *)(((char *)&pSMB->hdr.Protocol) + offset);
+ /* SMB offsets are from the beginning of SMB which is 4 bytes in,
after RFC1001 field */
+ pdata = (OPEN_PSX_REQ *)((char *)(pSMB) + offset + 4);
  pdata->Level = cpu_to_le16(SMB_QUERY_FILE_UNIX_BASIC);
  pdata->Permissions = cpu_to_le64(mode);
  pdata->PosixOpenFlags = cpu_to_le32(posix_flags);

-- 
Thanks,

Steve

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From 21a64910997e0c1d268bebf9b1217ba5804d592d Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@microsoft.com>
Date: Thu, 22 Jul 2021 13:50:41 -0500
Subject: [PATCH] CIFS: Clarify SMB1 code for POSIX Create

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 CIFSPOSIXCreate. This changeset
doesn't change the address but makes it slightly clearer.

Addresses-Coverity: 711518 ("Out of bounds write")
Signed-off-by: Steve French <stfrench@microsoft.com>
---
 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 f72e3b3dca69..d4144c182604 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -1081,7 +1081,8 @@ CIFSPOSIXCreate(const unsigned int xid, struct cifs_tcon *tcon,
 	param_offset = offsetof(struct smb_com_transaction2_spi_req,
 				InformationLevel) - 4;
 	offset = param_offset + params;
-	pdata = (OPEN_PSX_REQ *)(((char *)&pSMB->hdr.Protocol) + offset);
+	/* SMB offsets are from the beginning of SMB which is 4 bytes in, after RFC1001 field */
+	pdata = (OPEN_PSX_REQ *)((char *)(pSMB) + offset + 4);
 	pdata->Level = cpu_to_le16(SMB_QUERY_FILE_UNIX_BASIC);
 	pdata->Permissions = cpu_to_le64(mode);
 	pdata->PosixOpenFlags = cpu_to_le32(posix_flags);
-- 
2.30.2