dm crypt: fix async inc_pending

The pending reference count must be incremented *before* the async work is
queued to another thread, not after.  Otherwise there's a race if the
work completes and decrements the reference count before it gets incremented.

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

1 files changed, 2 insertions, 3 deletions

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index d8126ac82960..262ed1816695 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -719,16 +719,15 @@ static void kcryptd_crypt_write_convert(struct dm_crypt_io *io)
 
                 remaining -= clone->bi_size;
 
+                crypt_inc_pending(io);
                 r = crypt_convert(cc, &io->ctx);
 
                 if (atomic_dec_and_test(&io->ctx.pending)) {
                         /* processed, no running async crypto  */
-                        crypt_inc_pending(io);
                         kcryptd_crypt_write_io_submit(io, r, 0);
                         if (unlikely(r < 0))
                                 break;
-                } else
-                        crypt_inc_pending(io);
+                }
 
                 /* out of memory -> run queues */
                 if (unlikely(remaining)) {