smatch stuff: dereferencing first then checking in SendReceive()

[Steve French]

On Sat, Mar 19, 2011 at 6:28 PM, Dan Carpenter <error27 at gmail.com> wrote:
> Smatch complains about this, but I don't know if it's a bug or not.
>
> fs/cifs/transport.c +791 SendReceive(106)
>        warn: variable dereferenced before check 'midQ->resp_buf'
>
>   780          receive_len = be32_to_cpu(midQ->resp_buf->smb_buf_length);
>                                          ^^^^^^^^^^^^^^^^
>        dereference
>   781
>   782          if (receive_len > CIFSMaxBufSize + MAX_CIFS_HDR_SIZE) {
>   783                  cERROR(1, "Frame too large received.  Length: %d  Xid: %d",
>   784                          receive_len, xid);
>   785                  rc = -EIO;
>   786                  goto out;
>   787          }
>   788
>   789          /* rcvd frame is ok */
>   790
>   791          if (midQ->resp_buf && out_buf
>                    ^^^^^^^^^^^^^^
>        checking for null
>
>   792              && (midQ->midState == MID_RESPONSE_RECEIVED)) {
>   793                  out_buf->smb_buf_length = cpu_to_be32(receive_len);
>
> regards,
> dan carpenter

Older kernels had the same (midQ->resp_buf == NULL)
check in the same place, and I don't see a way to get there with
midQ->resp_buf == NULL so that check on line
791 does look redundant check.

I will double check.



-- 
Thanks,

Steve