diff --git a/block/blk-mq.c b/block/blk-mq.c index 0418c695d047..ad1459c6fdcd 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2622,16 +2622,49 @@ static void blk_mq_remove_cpuhp(struct blk_mq_hw_ctx *hctx) &hctx->cpuhp_dead); } +/* + * Before freeing hw queue, clearing the flush request reference in + * tags->rqs[] for avoiding potential UAF. + */ +static void blk_mq_clear_flush_rq_mapping(struct blk_mq_tags *tags, + unsigned int queue_depth, struct request *flush_rq) +{ + int i; + unsigned long flags; + + /* The hw queue may not be mapped yet */ + if (!tags) + return; + + WARN_ON_ONCE(refcount_read(&flush_rq->ref) != 0); + + for (i = 0; i < queue_depth; i++) + cmpxchg(&tags->rqs[i], flush_rq, NULL); + + /* + * Wait until all pending iteration is done. + * + * Request reference is cleared and it is guaranteed to be observed + * after the ->lock is released. + */ + spin_lock_irqsave(&tags->lock, flags); + spin_unlock_irqrestore(&tags->lock, flags); +} + /* hctx->ctxs will be freed in queue's release handler */ static void blk_mq_exit_hctx(struct request_queue *q, struct blk_mq_tag_set *set, struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx) { + struct request *flush_rq = hctx->fq->flush_rq; + if (blk_mq_hw_queue_mapped(hctx)) blk_mq_tag_idle(hctx); + blk_mq_clear_flush_rq_mapping(set->tags[hctx_idx], + set->queue_depth, flush_rq); if (set->ops->exit_request) - set->ops->exit_request(set, hctx->fq->flush_rq, hctx_idx); + set->ops->exit_request(set, flush_rq, hctx_idx); if (set->ops->exit_hctx) set->ops->exit_hctx(hctx, hctx_idx);