dm crypt: wait for endio to complete before destruction

The following oops has been reported when dm-crypt runs over a loop device.

...
[   70.381058] Process loop0 (pid: 4268, ti=cf3b2000 task=cf1cc1f0 task.ti=cf3b2000)
...
[   70.381058] Call Trace:
[   70.381058]  [<d0d76601>] ? crypt_dec_pending+0x5e/0x62 [dm_crypt]
[   70.381058]  [<d0d767b8>] ? crypt_endio+0xa2/0xaa [dm_crypt]
[   70.381058]  [<d0d76716>] ? crypt_endio+0x0/0xaa [dm_crypt]
[   70.381058]  [<c01a2f24>] ? bio_endio+0x2b/0x2e
[   70.381058]  [<d0806530>] ? dec_pending+0x224/0x23b [dm_mod]
[   70.381058]  [<d08066e4>] ? clone_endio+0x79/0xa4 [dm_mod]
[   70.381058]  [<d080666b>] ? clone_endio+0x0/0xa4 [dm_mod]
[   70.381058]  [<c01a2f24>] ? bio_endio+0x2b/0x2e
[   70.381058]  [<c02bad86>] ? loop_thread+0x380/0x3b7
[   70.381058]  [<c02ba8a1>] ? do_lo_send_aops+0x0/0x165
[   70.381058]  [<c013754f>] ? autoremove_wake_function+0x0/0x33
[   70.381058]  [<c02baa06>] ? loop_thread+0x0/0x3b7

When a table is being replaced, it waits for I/O to complete
before destroying the mempool, but the endio function doesn't
call mempool_free() until after completing the bio.

Fix it by swapping the order of those two operations.

The same problem occurs in dm.c with md referenced after dec_pending.
Again, we swap the order.

Cc: stable@kernel.org
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 10 insertions, 7 deletions

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index ebab49f8cc1d..bfefd079a955 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -568,19 +568,22 @@ static void crypt_inc_pending(struct dm_crypt_io *io)
 static void crypt_dec_pending(struct dm_crypt_io *io)
 {
         struct crypt_config *cc = io->target->private;
+        struct bio *base_bio = io->base_bio;
+        struct dm_crypt_io *base_io = io->base_io;
+        int error = io->error;
 
         if (!atomic_dec_and_test(&io->pending))
                 return;
 
-        if (likely(!io->base_io))
-                bio_endio(io->base_bio, io->error);
+        mempool_free(io, cc->io_pool);
+
+        if (likely(!base_io))
+                bio_endio(base_bio, error);
         else {
-                if (io->error && !io->base_io->error)
-                        io->base_io->error = io->error;
-                crypt_dec_pending(io->base_io);
+                if (error && !base_io->error)
+                        base_io->error = error;
+                crypt_dec_pending(base_io);
         }
-
-        mempool_free(io, cc->io_pool);
 }
 
 /*