Fix corrupt SMB2 ioctl requests

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@gmail.com>

1 files changed, 17 insertions, 4 deletions

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index edccb5252462..6e1868611233 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) {
+                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;