Commit d9a02e01 authored by Mike Snitzer's avatar Mike Snitzer
Browse files

dm crypt: avoid accessing uninitialized tasklet 



When neither "no_read_workqueue" nor "no_write_workqueue" are enabled,
tasklet_trylock() in crypt_dec_pending() may still return false due to
an uninitialized state, and dm-crypt will unnecessarily do io completion
in io_queue workqueue instead of current context.

Fix this by adding an 'in_tasklet' flag to dm_crypt_io struct and
initialize it to false in crypt_io_init(). Set this flag to true in
kcryptd_queue_crypt() before calling tasklet_schedule(). If set
crypt_dec_pending() will punt io completion to a workqueue.

This also nicely avoids the tasklet_trylock/unlock hack when tasklets
aren't in use.

Fixes: 8e14f610 ("dm crypt: do not call bio_endio() from the dm-crypt tasklet")
Cc: stable@vger.kernel.org
Reported-by: default avatarHou Tao <houtao1@huawei.com>
Suggested-by: default avatarIgnat Korchagin <ignat@cloudflare.com>
Reviewed-by: default avatarIgnat Korchagin <ignat@cloudflare.com>
Signed-off-by: default avatarMike Snitzer <snitzer@kernel.org>
parent fb294b1c

drivers/md/dm-crypt.c

+9 −6
Original line number Diff line number Diff line
@@ -72,7 +72,9 @@ struct dm_crypt_io { 
	struct crypt_config *cc;

	struct bio *base_bio;

	u8 *integrity_metadata;

	bool integrity_metadata_from_pool;

	bool integrity_metadata_from_pool:1;

	bool in_tasklet:1;



	struct work_struct work;

	struct tasklet_struct tasklet;
@@ -1731,6 +1733,7 @@ static void crypt_io_init(struct dm_crypt_io *io, struct crypt_config *cc, 
	io->ctx.r.req = NULL;

	io->integrity_metadata = NULL;

	io->integrity_metadata_from_pool = false;

	io->in_tasklet = false;

	atomic_set(&io->io_pending, 0);

}
@@ -1777,14 +1780,13 @@ static void crypt_dec_pending(struct dm_crypt_io *io) 
	 * our tasklet. In this case we need to delay bio_endio()

	 * execution to after the tasklet is done and dequeued.

	 */

	if (tasklet_trylock(&io->tasklet)) {

		tasklet_unlock(&io->tasklet);

		bio_endio(base_bio);

	if (io->in_tasklet) {

		INIT_WORK(&io->work, kcryptd_io_bio_endio);

		queue_work(cc->io_queue, &io->work);

		return;

	}



	INIT_WORK(&io->work, kcryptd_io_bio_endio);

	queue_work(cc->io_queue, &io->work);

	bio_endio(base_bio);

}



/*
@@ -2233,6 +2235,7 @@ static void kcryptd_queue_crypt(struct dm_crypt_io *io) 
		 * it is being executed with irqs disabled.

		 */

		if (in_hardirq() || irqs_disabled()) {

			io->in_tasklet = true;

			tasklet_init(&io->tasklet, kcryptd_crypt_tasklet, (unsigned long)&io->work);

			tasklet_schedule(&io->tasklet);

			return;