diff options
| author | Yu Kuai <yukuai3@huawei.com> | 2023-01-19 19:03:48 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2023-01-29 15:19:04 -0700 |
| commit | c7241babf0855d8a6180cd1743ff0ec34de40b4e (patch) | |
| tree | 6733e7f5513b5ff9752dc352f69c6b0a7c01dc9c | |
| parent | b36781034c42f9932bc6305e9a06490d61d9b8ff (diff) | |
blk-cgroup: dropping parent refcount after pd_free_fn() is done
Some cgroup policies will access parent pd through child pd even
after pd_offline_fn() is done. If pd_free_fn() for parent is called
before child, then UAF can be triggered. Hence it's better to guarantee
the order of pd_free_fn().
Currently refcount of parent blkg is dropped in __blkg_release(), which
is before pd_free_fn() is called in blkg_free_work_fn() while
blkg_free_work_fn() is called asynchronously.
This patch make sure pd_free_fn() called from removing cgroup is ordered
by delaying dropping parent refcount after calling pd_free_fn() for
child.
BTW, pd_free_fn() will also be called from blkcg_deactivate_policy()
from deleting device, and following patches will guarantee the order.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230119110350.2287325-2-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | block/blk-cgroup.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 4c94a6560f62..c6d7d1fce65a 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -124,6 +124,8 @@ static void blkg_free_workfn(struct work_struct *work) if (blkg->pd[i]) blkcg_policy[i]->pd_free_fn(blkg->pd[i]); + if (blkg->parent) + blkg_put(blkg->parent); if (blkg->q) blk_put_queue(blkg->q); free_percpu(blkg->iostat_cpu); @@ -158,8 +160,6 @@ static void __blkg_release(struct rcu_head *rcu) /* release the blkcg and parent blkg refs this blkg has been holding */ css_put(&blkg->blkcg->css); - if (blkg->parent) - blkg_put(blkg->parent); blkg_free(blkg); } |