Messages in this thread | | | Date | Fri, 14 Jan 2022 23:54:48 +0800 | From | Ming Lei <> | Subject | Re: [syzbot] KASAN: use-after-free Read in srcu_invoke_callbacks |
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On Fri, Jan 14, 2022 at 10:38:42PM +0800, Boqun Feng wrote: > Hi, > > On Tue, Jan 11, 2022 at 11:05:00AM -0800, Paul E. McKenney wrote: > [...] > > > > The buggy address belongs to the object at ffff8880189b5c70 > > > > which belongs to the cache request_queue_srcu of size 3816 > > This cache name drew my attention when I was trying to look into this, > because I couldn't find it in v5.16, later on I realized the UAF was > found in linux-next and the commit introducing the cache was merged into > mainline if 5.17 merge window: > > 704b914f15fb blk-mq: move srcu from blk_mq_hw_ctx to request_queue > > I think the UAF is actually a bug introduced by the commit, because in > that commit srcu structure was moved from blk_mq_hw_ctx to > request_queue, and therefore the cleanup_srcu_struct() should be moved > from blk_mq_hw_sysfs_release() to blk_release_queue(), however the above > commit only deleted the one in blk_mq_hw_sysfs_release() but didn't add > a new one in blk_release_queue(). As a result when a request queue is > freed, the srcu structure is not fully clean up, therefore the UAF. > > IOW, something like below (untested) should fix this. Copy the auther > and block maintainers. > > Regards, > Boqun > > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c > index e20eadfcf5c8..10f59416376e 100644 > --- a/block/blk-sysfs.c > +++ b/block/blk-sysfs.c > @@ -812,6 +812,10 @@ static void blk_release_queue(struct kobject *kobj) > bioset_exit(&q->bio_split); > > ida_simple_remove(&blk_queue_ida, q->id); > + > + if (test_bit(QUEUE_FLAG_HAS_SRCU, &q->queue_flags)) { > + cleanup_srcu_struct(q->srcu); > + } > call_rcu(&q->rcu_head, blk_free_queue_rcu); > }
Yes, this fix has been posted days ago:
https://lore.kernel.org/linux-block/20220111123401.520192-1-ming.lei@redhat.com/T/#u
Thanks, Ming
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