4.16-stable review patch. If anyone has any objections, please let me know.
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From: Jiang Biao jiang.biao2@zte.com.cn
[ Upstream commit 901932a3f9b2b80352896be946c6d577c0a9652c ]
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 jiang.biao2@zte.com.cn Signed-off-by: Wen Yang wen.yang99@zte.com.cn CC: Tejun Heo tj@kernel.org CC: Jens Axboe axboe@kernel.dk 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-cgroup.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-)
--- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1142,18 +1142,16 @@ int blkcg_init_queue(struct request_queu 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); @@ -1161,6 +1159,13 @@ int blkcg_init_queue(struct request_queu 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); }
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