From: Ming Lei ming.lei@redhat.com
[ Upstream commit fb350e0ad99359768e1e80b4784692031ec340e4 ]
In both elevator_switch_mq() and blk_mq_update_nr_hw_queues(), sched tags can be allocated, and q->nr_hw_queue is used, and race is inevitable, for example: blk_mq_init_sched() may trigger use-after-free on hctx, which is freed in blk_mq_realloc_hw_ctxs() when nr_hw_queues is decreased.
This patch fixes the race be holding q->sysfs_lock.
Reviewed-by: Christoph Hellwig hch@lst.de Reported-by: Yi Zhang yi.zhang@redhat.com Tested-by: Yi Zhang yi.zhang@redhat.com Signed-off-by: Ming Lei ming.lei@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- block/blk-mq.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/block/blk-mq.c b/block/blk-mq.c index 12bb7a49c5ba..c28d6b3088a0 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2314,6 +2314,9 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set, struct blk_mq_hw_ctx **hctxs = q->queue_hw_ctx;
blk_mq_sysfs_unregister(q); + + /* protect against switching io scheduler */ + mutex_lock(&q->sysfs_lock); for (i = 0; i < set->nr_hw_queues; i++) { int node;
@@ -2358,6 +2361,7 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set, } } q->nr_hw_queues = i; + mutex_unlock(&q->sysfs_lock); blk_mq_sysfs_register(q); }