FAILED: patch "[PATCH] dm crypt: avoid accessing uninitialized tasklet" failed to apply to 5.10-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x d9a02e016aaf5a57fb44e9a5e6da8ccd3b9e2e70
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '168000726237133@xxxxxxxxx' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

d9a02e016aaf ("dm crypt: avoid accessing uninitialized tasklet")
d3703ef33129 ("dm crypt: use in_hardirq() instead of deprecated in_irq()")
c87a95dc28b1 ("dm crypt: defer decryption to a tasklet if interrupts disabled")
8e14f610159d ("dm crypt: do not call bio_endio() from the dm-crypt tasklet")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From d9a02e016aaf5a57fb44e9a5e6da8ccd3b9e2e70 Mon Sep 17 00:00:00 2001
From: Mike Snitzer <snitzer@xxxxxxxxxx>
Date: Wed, 8 Mar 2023 14:39:54 -0500
Subject: [PATCH] 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: 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>

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index faba1be572f9..2764b4ea18a3 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -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;