Patch "dm: fix dm_rq_target_io leak on faults with .request_fn DM w/ blk-mq paths" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    dm: fix dm_rq_target_io leak on faults with .request_fn DM w/ blk-mq paths

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     dm-fix-dm_rq_target_io-leak-on-faults-with-.request_fn-dm-w-blk-mq-paths.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 4328daa2e79ed904a42ce00a9f38b9c36b44b21a Mon Sep 17 00:00:00 2001
From: Mike Snitzer <snitzer@redhat.com>
Date: Sun, 21 Feb 2016 19:09:22 -0500
Subject: dm: fix dm_rq_target_io leak on faults with .request_fn DM w/ blk-mq paths

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);
 }
 
 /*


Patches currently in stable-queue which might be from snitzer@redhat.com are

queue-4.4/dm-snapshot-fix-hung-bios-when-copy-error-occurs.patch
queue-4.4/dm-space-map-metadata-remove-unused-variable-in-brb_pop.patch
queue-4.4/dm-fix-dm_rq_target_io-leak-on-faults-with-.request_fn-dm-w-blk-mq-paths.patch
queue-4.4/dm-thin-fix-race-condition-when-destroying-thin-pool-workqueue.patch