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blk-throttle: fix throtl_data leak during disk release

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[ Upstream commit 336aec7b06 ]

Tightening the throttle activation check in blk_throtl_activated() to
require both q->td presence and policy bit set introduced a memory leak
during disk release:

blkg_destroy_all() clears the policy bit first during queue deactivation,
causing subsequent blk_throtl_exit() to skip throtl_data cleanup when
blk_throtl_activated() fails policy check.

Idealy we should avoid modifying blk_throtl_exit() activation check because
it's intuitive that blk-throtl start from blk_throtl_init() and end in
blk_throtl_exit(). However, call blk_throtl_exit() before
blkg_destroy_all() will make a long term deadlock problem easier to
trigger[1], hence fix this problem by checking if q->td is NULL from
blk_throtl_exit(), and remove policy deactivation as well since it's
useless.

[1] https://lore.kernel.org/all/CAHj4cs9p9H5yx+ywsb3CMUdbqGPhM+8tuBvhW=9ADiCjAqza9w@mail.gmail.com/#t

Fixes: bd9fd5be6b ("blk-throttle: fix access race during throttle policy activation")
Reported-by: Yi Zhang <yi.zhang@redhat.com>
Closes: https://lore.kernel.org/all/CAHj4cs-p-ZwBEKigBj7T6hQCOo-H68-kVwCrV6ZvRovrr9Z+HA@mail.gmail.com/
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Yu Kuai 2025-09-17 15:55:39 +08:00 committed by Greg Kroah-Hartman
parent 8e00ca2213
commit 76c6babc71
1 changed files with 5 additions and 2 deletions
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7
block/blk-throttle.c
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@ -1842,12 +1842,15 @@ void blk_throtl_exit(struct gendisk *disk)
{
struct request_queue *q = disk->queue;
if (!blk_throtl_activated(q))
/*
* blkg_destroy_all() already deactivate throtl policy, just check and
* free throtl data.
*/
if (!q->td)
return;
timer_delete_sync(&q->td->service_queue.pending_timer);
throtl_shutdown_wq(q);
blkcg_deactivate_policy(disk, &blkcg_policy_throtl);
kfree(q->td);
}