[PATCH 3.19 137/177] dm crypt: fix deadlock when async crypto algorithm returns -EBUSY

From: Greg Kroah-Hartman
Date: Sat May 02 2015 - 15:39:54 EST


3.19-stable review patch. If anyone has any objections, please let me know.

------------------

From: Ben Collins <ben.c@xxxxxxxxxxxx>

commit 0618764cb25f6fa9fb31152995de42a8a0496475 upstream.

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@xxxxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
drivers/md/dm-crypt.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -920,11 +920,10 @@ static int crypt_convert(struct crypt_co

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;
@@ -1315,10 +1314,8 @@ static void kcryptd_async_done(struct cr
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);
@@ -1329,12 +1326,15 @@ static void kcryptd_async_done(struct cr
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)


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