blkg_destroy_all() iterates q->blkg_list without holding blkcg_mutex, which can race with blkg_free_workfn() that removes blkgs from the list while holding blkcg_mutex. Add blkcg_mutex protection around the q->blkg_list iteration to prevent potential list corruption or use-after-free issues. Signed-off-by: Yu Kuai --- block/blk-cgroup.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 554c87bb4a86..a98a22e06fd1 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -573,10 +573,11 @@ static void blkg_destroy_all(struct gendisk *disk) struct blkcg_gq *blkg; int count = BLKG_DESTROY_BATCH_SIZE; int i; restart: + mutex_lock(&q->blkcg_mutex); spin_lock_irq(&q->queue_lock); list_for_each_entry(blkg, &q->blkg_list, q_node) { struct blkcg *blkcg = blkg->blkcg; if (hlist_unhashed(&blkg->blkcg_node)) @@ -591,10 +592,11 @@ static void blkg_destroy_all(struct gendisk *disk) * it when a batch of blkgs are destroyed. */ if (!(--count)) { count = BLKG_DESTROY_BATCH_SIZE; spin_unlock_irq(&q->queue_lock); + mutex_unlock(&q->blkcg_mutex); cond_resched(); goto restart; } } @@ -610,10 +612,11 @@ static void blkg_destroy_all(struct gendisk *disk) __clear_bit(pol->plid, q->blkcg_pols); } q->root_blkg = NULL; spin_unlock_irq(&q->queue_lock); + mutex_unlock(&q->blkcg_mutex); wake_up_var(&q->root_blkg); } static void blkg_iostat_set(struct blkg_iostat *dst, struct blkg_iostat *src) -- 2.51.0