From ee37eddbfa9e0401f13a01691cf4bbbacd2d16c9 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Fri, 18 Mar 2022 21:01:42 +0800 Subject: [PATCH] block: avoid use-after-free on throttle data In throtl_pending_timer_fn(), request queue is retrieved from throttle data. And tg's pending timer is deleted synchronously when releasing the associated blkg, at that time, throttle data may have been freed since commit 1059699f87eb ("block: move blkcg initialization/destroy into disk allocation/release handler") moves freeing q->td to disk_release() from blk_release_queue(). So use-after-free on q->td in throtl_pending_timer_fn can be triggered. Fixes the issue by: - do nothing in case that disk is released, when there isn't any bio to dispatch - retrieve request queue from blkg instead of throttle data for non top-level pending timer. Signed-off-by: Ming Lei Link: https://lore.kernel.org/r/20220318130144.1066064-2-ming.lei@redhat.com Signed-off-by: Jens Axboe --- block/blk-throttle.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/block/blk-throttle.c b/block/blk-throttle.c index a3b3ebc72dd4..880701d0106f 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -1137,12 +1137,22 @@ static void throtl_pending_timer_fn(struct timer_list *t) struct throtl_service_queue *sq = from_timer(sq, t, pending_timer); struct throtl_grp *tg = sq_to_tg(sq); struct throtl_data *td = sq_to_td(sq); - struct request_queue *q = td->queue; struct throtl_service_queue *parent_sq; + struct request_queue *q; bool dispatched; int ret; + /* throtl_data may be gone, so figure out request queue by blkg */ + if (tg) + q = tg->pd.blkg->q; + else + q = td->queue; + spin_lock_irq(&q->queue_lock); + + if (!q->root_blkg) + goto out_unlock; + if (throtl_can_upgrade(td, NULL)) throtl_upgrade_state(td); -- 2.25.1