Messages in this thread |  | | Subject | Re: [RFC 0/3] block: address blktrace use-after-free | From | "yukuai (C)" <> | Date | Tue, 7 Apr 2020 10:47:01 +0800 |
| |
On 2020/4/3 16:19, Ming Lei wrote:
> BTW, Yu Kuai posted one patch for this issue, looks that approach > is simpler: > > https://lore.kernel.org/linux-block/20200324132315.22133-1-yukuai3@huawei.com/ > >
I think the issue might not be fixed with the patch seires.
At first, I think there are two key points for the issure: 1. The final release of queue is delayed in a workqueue 2. The creation of 'q->debugfs_dir' might failed(only if 1 exist) And if we can fix any of the above problem, the UAF issue will be fixed. (BTW, I did not come up with a good idea for problem 1, and my approach is for problem 2.)
The third patch "block: avoid deferral of blk_release_queue() work" is not enough to fix problem 1: a. if CONFIG_DEBUG_KOBJECT_RELEASE is enable: static void kobject_release(struct kref *kref) { struct kobject *kobj = container_of(kref, struct kobject, kref); #ifdef CONFIG_DEBUG_KOBJECT_RELEASE unsigned long delay = HZ + HZ * (get_random_int() & 0x3); pr_info("kobject: '%s' (%p): %s, parent %p (delayed %ld)\n", ┊kobject_name(kobj), kobj, __func__, kobj->parent, delay); INIT_DELAYED_WORK(&kobj->release, kobject_delayed_cleanup);
schedule_delayed_work(&kobj->release, delay); #else kobject_cleanup(kobj); #endif } b. when 'kobject_put' is called from blk_cleanup_queue, can we make sure it is the last reference?
Futhermore, I do understand the second patch fix the UAF problem by using 'q->debugfs_dir' instead of 'q->blk_trace->dir', but the problem 2 still exist and need to be fixed.
Thanks! Yu Kuai
|  |