From: Yu Kuai Date: Wed, 17 Sep 2025 07:55:39 +0000 (+0800) Subject: blk-throttle: fix throtl_data leak during disk release X-Git-Tag: v6.18-rc1~136^2~28 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=336aec7b06be860477be80a4299263a2e9355789;p=thirdparty%2Fkernel%2Flinux.git blk-throttle: fix throtl_data leak during disk release 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: bd9fd5be6bc0 ("blk-throttle: fix access race during throttle policy activation") Reported-by: Yi Zhang Closes: https://lore.kernel.org/all/CAHj4cs-p-ZwBEKigBj7T6hQCOo-H68-kVwCrV6ZvRovrr9Z+HA@mail.gmail.com/ Signed-off-by: Yu Kuai Signed-off-by: Jens Axboe --- diff --git a/block/blk-throttle.c b/block/blk-throttle.c index f510ae072868c..2c5b64b1a724a 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -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); }