linux-kernel - [PATCH 3.16 004/204] cifs: check rsp for NULL before dereferencing in SMB2

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Date:   Thu, 28 Dec 2017 17:05:44 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Pavel Shilovsky" <pshilov@...rosoft.com>,
        "Xiaoli Feng" <xifeng@...hat.com>,
        "Ronnie Sahlberg" <lsahlber@...hat.com>,
        "Steve French" <smfrench@...il.com>
Subject: [PATCH 3.16 004/204] cifs: check rsp for NULL before
 dereferencing in SMB2_open

3.16.52-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ronnie Sahlberg <lsahlber@...hat.com>

commit bf2afee14e07de16d3cafc67edbfc2a3cc65e4bc upstream.

In SMB2_open there are several paths where the SendReceive2
call will return an error before it sets rsp_iov.iov_base
thus leaving iov_base uninitialized.

Thus we need to check rsp before we dereference it in
the call to get_rfc1002_length().

A report of this issue was previously reported in
http://www.spinics.net/lists/linux-cifs/msg12846.html

RH-bugzilla : 1476151

Version 2 :
* Lets properly initialize rsp_iov before we use it.

Signed-off-by: Ronnie Sahlberg <lsahlber@...hat.com>
Reviewed-by: Pavel Shilovsky <pshilov@...rosoft.com>.
Signed-off-by: Steve French <smfrench@...il.com>
Reported-by: Xiaoli Feng <xifeng@...hat.com>
[bwh: Backported to 3.16: zero-initialise iov instead of rsp_iov]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/cifs/smb2pdu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -1114,7 +1114,7 @@ SMB2_open(const unsigned int xid, struct
 	struct TCP_Server_Info *server;
 	struct cifs_tcon *tcon = oparms->tcon;
 	struct cifs_ses *ses = tcon->ses;
-	struct kvec iov[4];
+	struct kvec iov[4] = {{NULL, 0}};
 	int resp_buftype;
 	int uni_path_len;
 	__le16 *copy_path = NULL;
@@ -1215,7 +1215,7 @@ SMB2_open(const unsigned int xid, struct
 
 	if (rc != 0) {
 		cifs_stats_fail_inc(tcon, SMB2_CREATE_HE);
-		if (err_buf)
+		if (err_buf && rsp)
 			*err_buf = kmemdup(rsp, get_rfc1002_length(rsp) + 4,
 					   GFP_KERNEL);
 		goto creat_exit;