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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: 8e14f61015 ("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>
This commit is contained in:
Mike Snitzer 2023-03-08 14:39:54 -05:00
parent fb294b1c0b
commit d9a02e016a
1 changed files with 9 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
drivers/md/dm-crypt.c
View File

@ -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;