[dm-devel] Patch "dm crypt: avoid accessing uninitialized tasklet" has been added to the 5.10-stable tree

[Sasha Levin <sashal@kernel.org>]

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

    dm crypt: avoid accessing uninitialized tasklet

to the 5.10-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-5.10 subdirectory.

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



commit a95530ebdb4ef34ea248ae061d1fd676a6d4cc8e
Author: Mike Snitzer <snitzer@kernel.org>
Date:   Wed Mar 8 14:39:54 2023 -0500

    dm crypt: avoid accessing uninitialized tasklet
    
    [ Upstream commit d9a02e016aaf5a57fb44e9a5e6da8ccd3b9e2e70 ]
    
    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@vger.kernel.org
    Reported-by: Hou Tao <houtao1@huawei.com>
    Suggested-by: Ignat Korchagin <ignat@cloudflare.com>
    Reviewed-by: Ignat Korchagin <ignat@cloudflare.com>
    Signed-off-by: Mike Snitzer <snitzer@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 17ddca293965c..5d772f322a245 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -67,7 +67,9 @@ 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;
 
@@ -1722,6 +1724,7 @@ 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);
 }
 
@@ -1767,14 +1770,13 @@ 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);
 }
 
 /*
@@ -2228,6 +2230,7 @@ static void kcryptd_queue_crypt(struct dm_crypt_io *io)
 		 * it is being executed with irqs disabled.
 		 */
 		if (in_irq() || irqs_disabled()) {
+			io->in_tasklet = true;
 			tasklet_init(&io->tasklet, kcryptd_crypt_tasklet, (unsigned long)&io->work);
 			tasklet_schedule(&io->tasklet);
 			return;

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