From f0c1c4d2864ed614f90d2da1bab1a1c42907b940 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Wed, 9 Jun 2021 14:30:46 +0800 Subject: blk-mq: fix use-after-free in blk_mq_exit_sched tagset can't be used after blk_cleanup_queue() is returned because freeing tagset usually follows blk_clenup_queue(). Commit d97e594c5166 ("blk-mq: Use request queue-wide tags for tagset-wide sbitmap") adds check on q->tag_set->flags in blk_mq_exit_sched(), and causes use-after-free. Fixes it by using hctx->flags. Reported-by: syzbot+77ba3d171a25c56756ea@syzkaller.appspotmail.com Fixes: d97e594c5166 ("blk-mq: Use request queue-wide tags for tagset-wide sbitmap") Cc: John Garry Signed-off-by: Ming Lei Tested-by: John Garry Reviewed-by: John Garry Link: https://lore.kernel.org/r/20210609063046.122843-1-ming.lei@redhat.com Signed-off-by: Jens Axboe --- block/blk-mq-sched.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'block/blk-mq-sched.c') diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index a9182d2f8ad3..80273245d11a 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -680,6 +680,7 @@ void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e) { struct blk_mq_hw_ctx *hctx; unsigned int i; + unsigned int flags = 0; queue_for_each_hw_ctx(q, hctx, i) { blk_mq_debugfs_unregister_sched_hctx(hctx); @@ -687,12 +688,13 @@ void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e) e->type->ops.exit_hctx(hctx, i); hctx->sched_data = NULL; } + flags = hctx->flags; } blk_mq_debugfs_unregister_sched(q); if (e->type->ops.exit_sched) e->type->ops.exit_sched(e); blk_mq_sched_tags_teardown(q); - if (blk_mq_is_sbitmap_shared(q->tag_set->flags)) + if (blk_mq_is_sbitmap_shared(flags)) blk_mq_exit_sched_shared_sbitmap(q); q->elevator = NULL; } -- cgit