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authorMing Lei <ming.lei@redhat.com>2018-01-06 16:27:40 +0800
committerJens Axboe <axboe@kernel.dk>2018-01-06 09:25:36 -0700
commitfb350e0ad99359768e1e80b4784692031ec340e4 (patch)
tree25d87e34b68ada63eb442c6269b031f037011520 /block/blk-mq.c
parent7d4901a90d02500c8011472a060f9b2e60e6e605 (diff)
blk-mq: fix race between updating nr_hw_queues and switching io sched
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>
Diffstat (limited to 'block/blk-mq.c')
-rw-r--r--block/blk-mq.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index dd21051fb251..111e1aa5562f 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2407,6 +2407,9 @@ 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;
@@ -2451,6 +2454,7 @@ 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);
}