From: Jiang Biao Date: Thu, 19 Apr 2018 04:06:09 +0000 (+0800) Subject: blkcg: init root blkcg_gq under lock X-Git-Tag: v4.17-rc3~35^2~4 X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=901932a3f9b2b80352896be946c6d577c0a9652c;p=uclinux-h8%2Flinux.git blkcg: init root blkcg_gq under lock The initializing of q->root_blkg is currently outside of queue lock and rcu, so the blkg may be destroied before the initializing, which may cause dangling/null references. On the other side, the destroys of blkg are protected by queue lock or rcu. Put the initializing inside the queue lock and rcu to make it safer. Signed-off-by: Jiang Biao Signed-off-by: Wen Yang CC: Tejun Heo CC: Jens Axboe Signed-off-by: Jens Axboe --- diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 79da2a723b68..eb85cb87c40f 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1181,18 +1181,16 @@ int blkcg_init_queue(struct request_queue *q) rcu_read_lock(); spin_lock_irq(q->queue_lock); blkg = blkg_create(&blkcg_root, q, new_blkg); + if (IS_ERR(blkg)) + goto err_unlock; + q->root_blkg = blkg; + q->root_rl.blkg = blkg; spin_unlock_irq(q->queue_lock); rcu_read_unlock(); if (preloaded) radix_tree_preload_end(); - if (IS_ERR(blkg)) - return PTR_ERR(blkg); - - q->root_blkg = blkg; - q->root_rl.blkg = blkg; - ret = blk_throtl_init(q); if (ret) { spin_lock_irq(q->queue_lock); @@ -1200,6 +1198,13 @@ int blkcg_init_queue(struct request_queue *q) spin_unlock_irq(q->queue_lock); } return ret; + +err_unlock: + spin_unlock_irq(q->queue_lock); + rcu_read_unlock(); + if (preloaded) + radix_tree_preload_end(); + return PTR_ERR(blkg); } /**