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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 d97e594c51
("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: d97e594c51 ("blk-mq: Use request queue-wide tags for tagset-wide sbitmap")
Cc: John Garry <john.garry@huawei.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Tested-by: John Garry <john.garry@huawei.com>
Reviewed-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/20210609063046.122843-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2021-06-09 14:30:46 +08:00 committed by Jens Axboe
parent 828615950b
commit f0c1c4d286
1 changed files with 3 additions and 1 deletions
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4
block/blk-mq-sched.c
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@ -680,6 +680,7 @@ void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e)
{ {
struct blk_mq_hw_ctx *hctx; struct blk_mq_hw_ctx *hctx;
unsigned int i; unsigned int i;
unsigned int flags = 0;
queue_for_each_hw_ctx(q, hctx, i) { queue_for_each_hw_ctx(q, hctx, i) {
blk_mq_debugfs_unregister_sched_hctx(hctx); 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); e->type->ops.exit_hctx(hctx, i);
hctx->sched_data = NULL; hctx->sched_data = NULL;
} }
flags = hctx->flags;
} }
blk_mq_debugfs_unregister_sched(q); blk_mq_debugfs_unregister_sched(q);
if (e->type->ops.exit_sched) if (e->type->ops.exit_sched)
e->type->ops.exit_sched(e); e->type->ops.exit_sched(e);
blk_mq_sched_tags_teardown(q); 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); blk_mq_exit_sched_shared_sbitmap(q);
q->elevator = NULL; q->elevator = NULL;
} }