From: Ignat Korchagin <ig...@cloudflare.com>
commit 8e14f610159d524cd7aac37982826d3ef75c09e8 upstream.
Sometimes, when dm-crypt executes decryption in a tasklet, we may get
"BUG: KASAN: use-after-free in tasklet_action_common.constprop..."
with a kasan-enabled kernel.
When the decryption fully completes in the tasklet, dm-crypt will call
bio_endio(), which in turn will call clone_endio() from dm.c core code. That
function frees the resources associated with the bio, including per bio private
structures. For dm-crypt it will free the current struct dm_crypt_io, which
contains our tasklet object, causing use-after-free, when the tasklet is being
dequeued by the kernel.
To avoid this, do not call bio_endio() from the current tasklet context, but
delay its execution to the dm-crypt IO workqueue.
Fixes: 39d42fa96ba1 ("dm crypt: add flags to optionally bypass kcryptd
workqueues")
Cc: <sta...@vger.kernel.org> # v5.9+
Signed-off-by: Ignat Korchagin <ig...@cloudflare.com>
Signed-off-by: Mike Snitzer <snit...@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
drivers/md/dm-crypt.c | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -1730,6 +1730,12 @@ static void crypt_inc_pending(struct dm_
atomic_inc(&io->io_pending);
}
+static void kcryptd_io_bio_endio(struct work_struct *work)
+{
+ struct dm_crypt_io *io = container_of(work, struct dm_crypt_io, work);
+ bio_endio(io->base_bio);
+}
+
/*
* One of the bios was finished. Check for completion of
* the whole request and correctly clean up the buffer.
@@ -1752,7 +1758,23 @@ static void crypt_dec_pending(struct dm_
kfree(io->integrity_metadata);
base_bio->bi_status = error;
- bio_endio(base_bio);
+
+ /*
+ * If we are running this function from our tasklet,
+ * we can't call bio_endio() here, because it will call
+ * clone_endio() from dm.c, which in turn will
+ * free the current struct dm_crypt_io structure with
+ * 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);
+ return;
+ }
+
+ INIT_WORK(&io->work, kcryptd_io_bio_endio);
+ queue_work(cc->io_queue, &io->work);
}
/*
