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    Subject[PATCH 4.5 053/238] dm: fix rq_end_stats() NULL pointer in dm_requeue_original_request()
    Date
    4.5-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Bryn M. Reeves <bmr@redhat.com>

    commit 98dbc9c6c61698792e3a66f32f3bf066201d42d7 upstream.

    An "old" (.request_fn) DM 'struct request' stores a pointer to the
    associated 'struct dm_rq_target_io' in rq->special.

    dm_requeue_original_request(), previously named
    dm_requeue_unmapped_original_request(), called dm_unprep_request() to
    reset rq->special to NULL. But rq_end_stats() would go on to hit a NULL
    pointer deference because its call to tio_from_request() returned NULL.

    Fix this by calling rq_end_stats() _before_ dm_unprep_request()

    Signed-off-by: Bryn M. Reeves <bmr@redhat.com>
    Signed-off-by: Mike Snitzer <snitzer@redhat.com>
    Fixes: e262f34741 ("dm stats: add support for request-based DM devices")
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/md/dm.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/drivers/md/dm.c
    +++ b/drivers/md/dm.c
    @@ -1210,9 +1210,9 @@ static void dm_requeue_original_request(
    {
    int rw = rq_data_dir(rq);

    + rq_end_stats(md, rq);
    dm_unprep_request(rq);

    - rq_end_stats(md, rq);
    if (!rq->q->mq_ops)
    old_requeue_request(rq);
    else {

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