[PATCH 6.1 218/224] dm crypt: avoid accessing uninitialized tasklet

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From: Mike Snitzer <snitzer@xxxxxxxxxx>

commit d9a02e016aaf5a57fb44e9a5e6da8ccd3b9e2e70 upstream.

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: 8e14f610159d ("dm crypt: do not call bio_endio() from the dm-crypt tasklet")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Hou Tao <houtao1@xxxxxxxxxx>
Suggested-by: Ignat Korchagin <ignat@xxxxxxxxxxxxxx>
Reviewed-by: Ignat Korchagin <ignat@xxxxxxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
 drivers/md/dm-crypt.c |   15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -71,7 +71,9 @@ 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;
@@ -1728,6 +1730,7 @@ static void crypt_io_init(struct dm_cryp
 	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);
@@ -1773,14 +1776,13 @@ static void crypt_dec_pending(struct dm_
 	 * 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);
-	INIT_WORK(&io->work, kcryptd_io_bio_endio);
-	queue_work(cc->io_queue, &io->work);
+	bio_endio(base_bio);
@@ -2229,6 +2231,7 @@ static void kcryptd_queue_crypt(struct d
 		 * 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);

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