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    Subject[PATCH 4.4 124/342] dm: fix dm_rq_target_io leak on faults with .request_fn DM w/ blk-mq paths
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

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

    From: Mike Snitzer <snitzer@redhat.com>

    commit 4328daa2e79ed904a42ce00a9f38b9c36b44b21a upstream.

    Using request-based DM mpath configured with the following stacking
    (.request_fn DM mpath ontop of scsi-mq paths):

    echo Y > /sys/module/scsi_mod/parameters/use_blk_mq
    echo N > /sys/module/dm_mod/parameters/use_blk_mq

    'struct dm_rq_target_io' would leak if a request is requeued before a
    blk-mq clone is allocated (or fails to allocate). free_rq_tio()
    wasn't being called.

    kmemleak reported:

    unreferenced object 0xffff8800b90b98c0 (size 112):
    comm "kworker/7:1H", pid 5692, jiffies 4295056109 (age 78.589s)
    hex dump (first 32 bytes):
    00 d0 5c 2c 03 88 ff ff 40 00 bf 01 00 c9 ff ff ..\,....@.......
    e0 d9 b1 34 00 88 ff ff 00 00 00 00 00 00 00 00 ...4............
    backtrace:
    [<ffffffff81672b6e>] kmemleak_alloc+0x4e/0xb0
    [<ffffffff811dbb63>] kmem_cache_alloc+0xc3/0x1e0
    [<ffffffff8117eae5>] mempool_alloc_slab+0x15/0x20
    [<ffffffff8117ec1e>] mempool_alloc+0x6e/0x170
    [<ffffffffa00029ac>] dm_old_prep_fn+0x3c/0x180 [dm_mod]
    [<ffffffff812fbd78>] blk_peek_request+0x168/0x290
    [<ffffffffa0003e62>] dm_request_fn+0xb2/0x1b0 [dm_mod]
    [<ffffffff812f66e3>] __blk_run_queue+0x33/0x40
    [<ffffffff812f9585>] blk_delay_work+0x25/0x40
    [<ffffffff81096fff>] process_one_work+0x14f/0x3d0
    [<ffffffff81097715>] worker_thread+0x125/0x4b0
    [<ffffffff8109ce88>] kthread+0xd8/0xf0
    [<ffffffff8167cb8f>] ret_from_fork+0x3f/0x70
    [<ffffffffffffffff>] 0xffffffffffffffff

    crash> struct -o dm_rq_target_io
    struct dm_rq_target_io {
    ...
    }
    SIZE: 112

    Fixes: e5863d9ad7 ("dm: allocate requests in target when stacking on blk-mq devices")
    Signed-off-by: Mike Snitzer <snitzer@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

    --- a/drivers/md/dm.c
    +++ b/drivers/md/dm.c
    @@ -1191,6 +1191,8 @@ static void dm_unprep_request(struct req

    if (clone)
    free_rq_clone(clone);
    + else if (!tio->md->queue->mq_ops)
    + free_rq_tio(tio);
    }

    /*
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