[PATCH] [CIFS] Fix corrupt SMB2 ioctl requests

[Steve French]

Now that I have been able to test a wider variety of
SMB2/SMB3 ioctls, some with input payloads and
some without, I have this updated version of the patch
(which hopefully is cleaner )

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-***@public.gmane.org>
---
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 edccb52..afa3829 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -1137,6 +1137,7 @@ 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;
@@ -1182,11 +1183,23 @@ 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) {
+ inc_rfc1001_len(req, indatalen - 1);
+ iov[0].iov_len = get_rfc1002_length(req) + 4 - 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;