dm crypt: fix deadlock when async crypto algorithm returns -EBUSY

I suspect this doesn't show up for most anyone because software
algorithms typically don't have a sense of being too busy.  However,
when working with the Freescale CAAM driver it will return -EBUSY on
occasion under heavy -- which resulted in dm-crypt deadlock.

After checking the logic in some other drivers, the scheme for
crypt_convert() and it's callback, kcryptd_async_done(), were not
correctly laid out to properly handle -EBUSY or -EINPROGRESS.

Fix this by using the completion for both -EBUSY and -EINPROGRESS.  Now
crypt_convert()'s use of completion is comparable to
af_alg_wait_for_completion().  Similarly, kcryptd_async_done() follows
the pattern used in af_alg_complete().

Before this fix dm-crypt would lockup within 1-2 minutes running with
the CAAM driver.  Fix was regression tested against software algorithms
on PPC32 and x86_64, and things seem perfectly happy there as well.

Signed-off-by: Ben Collins <ben.c@servergy.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org

1 files changed, 6 insertions, 6 deletions

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index aa1238facbeb..9b5e1eb0ffcf 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -925,11 +925,10 @@ static int crypt_convert(struct crypt_config *cc,
 
                 switch (r) {
                 /* async */
+                case -EINPROGRESS:
                 case -EBUSY:
                         wait_for_completion(&ctx->restart);
                         reinit_completion(&ctx->restart);
-                        /* fall through*/
-                case -EINPROGRESS:
                         ctx->req = NULL;
                         ctx->cc_sector++;
                         continue;
@@ -1346,10 +1345,8 @@ static void kcryptd_async_done(struct crypto_async_request *async_req,
         struct dm_crypt_io *io = container_of(ctx, struct dm_crypt_io, ctx);
         struct crypt_config *cc = io->cc;
 
-        if (error == -EINPROGRESS) {
-                complete(&ctx->restart);
+        if (error == -EINPROGRESS)
                 return;
-        }
 
         if (!error && cc->iv_gen_ops && cc->iv_gen_ops->post)
                 error = cc->iv_gen_ops->post(cc, iv_of_dmreq(cc, dmreq), dmreq);
@@ -1360,12 +1357,15 @@ static void kcryptd_async_done(struct crypto_async_request *async_req,
         crypt_free_req(cc, req_of_dmreq(cc, dmreq), io->base_bio);
 
         if (!atomic_dec_and_test(&ctx->cc_pending))
-                return;
+                goto done;
 
         if (bio_data_dir(io->base_bio) == READ)
                 kcryptd_crypt_read_done(io);
         else
                 kcryptd_crypt_write_io_submit(io, 1);
+done:
+        if (!completion_done(&ctx->restart))
+                complete(&ctx->restart);
 }
 
 static void kcryptd_crypt(struct work_struct *work)