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

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index aa1238f..9b5e1eb 100644 (file)
--- 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)