[PATCH] CIFS: Clarify SMB1 code for UnixCreateSymLink

[PATCH] CIFS: Clarify SMB1 code for UnixCreateSymLink

[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 creating SMB1 symlinks when using the Unix
extensions.  This doesn't change the address but
makes it slightly clearer.

Addresses-Coverity: 711530 ("Out of bounds read")
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
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 ea12fa6eacb6..a14d3f533301 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -2925,7 +2925,8 @@ CIFSUnixCreateSymLink(const unsigned int xid,
struct cifs_tcon *tcon,
  InformationLevel) - 4;
  offset = param_offset + params;

- data_offset = (char *) (&pSMB->hdr.Protocol) + offset;
+ /* SMB offsets are from the beginning of SMB which is 4 bytes in,
after RFC1001 field */
+ data_offset = (char *)pSMB + offset + 4;
  if (pSMB->hdr.Flags2 & SMBFLG2_UNICODE) {
  name_len_target =
      cifsConvertToUTF16((__le16 *) data_offset, toName,

-- 
Thanks,

Steve

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From e7198dbf8b62296319690da591c396cf05d91c65 Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@microsoft.com>
Date: Thu, 1 Jul 2021 20:44:27 -0500
Subject: [PATCH] CIFS: Clarify SMB1 code for UnixCreateSymLink

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 creating SMB1 symlinks when using the Unix
extensions.  This doesn't change the address but
makes it slightly clearer.

Addresses-Coverity: 711529 ("Out of bounds read")
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
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 ea12fa6eacb6..a14d3f533301 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -2925,7 +2925,8 @@ CIFSUnixCreateSymLink(const unsigned int xid, struct cifs_tcon *tcon,
 				InformationLevel) - 4;
 	offset = param_offset + params;
 
-	data_offset = (char *) (&pSMB->hdr.Protocol) + offset;
+	/* SMB offsets are from the beginning of SMB which is 4 bytes in, after RFC1001 field */
+	data_offset = (char *)pSMB + offset + 4;
 	if (pSMB->hdr.Flags2 & SMBFLG2_UNICODE) {
 		name_len_target =
 		    cifsConvertToUTF16((__le16 *) data_offset, toName,
-- 
2.30.2