On Wed, Jul 11, 2012 at 6:28 AM, Sachin Prabhu <sprabhu@xxxxxxxxxx> wrote:
> A user reported a crash in cifs_demultiplex_thread() caused by an
> incorrectly set mid_q_entry->callback() function. It appears that the
> callback assignment made in cifs_call_async() was not flushed back to
> memory suggesting that a memory barrier was required here. Changing the
> code to make sure that the mid_q_entry structure was completely
> initialised before it was added to the pending queue fixes the problem.
>
> Signed-off-by: Sachin Prabhu <sprabhu@xxxxxxxxxx>
> ---
> fs/cifs/transport.c | 26 ++++++++++++++------------
> 1 file changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
> index 3097ee5..f25d4ea 100644
> --- a/fs/cifs/transport.c
> +++ b/fs/cifs/transport.c
> @@ -365,16 +365,14 @@ cifs_setup_async_request(struct TCP_Server_Info *server, struct kvec *iov,
> if (mid == NULL)
> return -ENOMEM;
>
> - /* put it on the pending_mid_q */
> - spin_lock(&GlobalMid_Lock);
> - list_add_tail(&mid->qhead, &server->pending_mid_q);
> - spin_unlock(&GlobalMid_Lock);
> -
> rc = cifs_sign_smb2(iov, nvec, server, &mid->sequence_number);
> - if (rc)
> - delete_mid(mid);
> + if (rc) {
> + DeleteMidQEntry(mid);
> + return rc;
> + }
> +
> *ret_mid = mid;
> - return rc;
> + return 0;
> }
>
> /*
> @@ -407,17 +405,21 @@ cifs_call_async(struct TCP_Server_Info *server, struct kvec *iov,
> mid->callback_data = cbdata;
> mid->mid_state = MID_REQUEST_SUBMITTED;
>
> + /* put it on the pending_mid_q */
> + spin_lock(&GlobalMid_Lock);
> + list_add_tail(&mid->qhead, &server->pending_mid_q);
> + spin_unlock(&GlobalMid_Lock);
> +
> +
> cifs_in_send_inc(server);
> rc = smb_sendv(server, iov, nvec);
> cifs_in_send_dec(server);
> cifs_save_when_sent(mid);
> mutex_unlock(&server->srv_mutex);
>
> - if (rc)
> - goto out_err;
> + if (rc == 0)
> + return 0;
>
> - return rc;
> -out_err:
> delete_mid(mid);
> add_credits(server, 1);
> wake_up(&server->request_q);
> --
> 1.7.10.4
>
Looks correct.
Reviewed-by: Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx>
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