Patch "dm crypt: avoid accessing uninitialized tasklet" has been added to the 6.1-stable tree

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This is a note to let you know that I've just added the patch titled

    dm crypt: avoid accessing uninitialized tasklet

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     dm-crypt-avoid-accessing-uninitialized-tasklet.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From d9a02e016aaf5a57fb44e9a5e6da8ccd3b9e2e70 Mon Sep 17 00:00:00 2001
From: Mike Snitzer <snitzer@xxxxxxxxxx>
Date: Wed, 8 Mar 2023 14:39:54 -0500
Subject: dm crypt: avoid accessing uninitialized tasklet

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);
 		return;
 	}
 
-	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);
 			tasklet_schedule(&io->tasklet);
 			return;


Patches currently in stable-queue which might be from snitzer@xxxxxxxxxx are

queue-6.1/dm-crypt-add-cond_resched-to-dmcrypt_write.patch
queue-6.1/dm-thin-fix-deadlock-when-swapping-to-thin-device.patch
queue-6.1/dm-stats-check-for-and-propagate-alloc_percpu-failure.patch
queue-6.1/dm-crypt-avoid-accessing-uninitialized-tasklet.patch



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