[PATCH 3.12 034/111] Fix corrupt SMB2 ioctl requests

[Jiri Slaby]

From: Steve French <smfrench@xxxxxxxxx>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 7ff8d45c9dccf0744404d6fe44468ede7c1b9533 upstream.

We were off by one calculating the length of ioctls in some cases
because the protocol specification for SMB2 ioctl includes a mininum
one byte payload but not all SMB2 ioctl requests actually have
a data buffer to send. We were also not zeroing out the
return buffer (in case of error this is helpful).

Signed-off-by: Steve French <smfrench@xxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 fs/cifs/smb2pdu.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 1f096f694030..1bf0ba805ef5 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -1228,6 +1228,7 @@ SMB2_ioctl(const unsigned int xid, struct cifs_tcon *tcon, u64 persistent_fid,
 
 	cifs_dbg(FYI, "SMB2 IOCTL\n");
 
+	*out_data = NULL;
 	/* zero out returned data len, in case of error */
 	if (plen)
 		*plen = 0;
@@ -1273,11 +1274,23 @@ SMB2_ioctl(const unsigned int xid, struct cifs_tcon *tcon, u64 persistent_fid,
 		req->Flags = 0;
 
 	iov[0].iov_base = (char *)req;
-	/* 4 for rfc1002 length field */
-	iov[0].iov_len = get_rfc1002_length(req) + 4;
 
-	if (indatalen)
-		inc_rfc1001_len(req, indatalen);
+	/*
+	 * If no input data, the size of ioctl struct in
+	 * protocol spec still includes a 1 byte data buffer,
+	 * but if input data passed to ioctl, we do not
+	 * want to double count this, so we do not send
+	 * the dummy one byte of data in iovec[0] if sending
+	 * input data (in iovec[1]). We also must add 4 bytes
+	 * in first iovec to allow for rfc1002 length field.
+	 */
+
+	if (indatalen) {
+		iov[0].iov_len = get_rfc1002_length(req) + 4 - 1;
+		inc_rfc1001_len(req, indatalen - 1);
+	} else
+		iov[0].iov_len = get_rfc1002_length(req) + 4;
+
 
 	rc = SendReceive2(xid, ses, iov, num_iovecs, &resp_buftype, 0);
 	rsp = (struct smb2_ioctl_rsp *)iov[0].iov_base;
-- 
2.4.2

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