| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.15 053/168] blk-mq: fix race between updating nr_hw_queues and switching io sched | Date | Wed, 11 Apr 2018 00:23:15 +0200 |
| |
4.15-stable review patch. If anyone has any objections, please let me know.
------------------
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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- block/blk-mq.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2388,6 +2388,9 @@ static void blk_mq_realloc_hw_ctxs(struc 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; @@ -2432,6 +2435,7 @@ static void blk_mq_realloc_hw_ctxs(struc } } q->nr_hw_queues = i; + mutex_unlock(&q->sysfs_lock); blk_mq_sysfs_register(q); }
|