Messages in this thread | | | Subject | Re: [locks] 6d390e4b5d: will-it-scale.per_process_ops -96.6% regression | From | yangerkun <> | Date | Wed, 18 Mar 2020 09:09:13 +0800 |
| |
On 2020/3/18 0:07, Jeff Layton wrote: > On Tue, 2020-03-17 at 22:05 +0800, yangerkun wrote: >> >> On 2020/3/17 9:41, yangerkun wrote: >>> >>> On 2020/3/17 1:26, Linus Torvalds wrote: >>>> On Mon, Mar 16, 2020 at 4:07 AM Jeff Layton <jlayton@kernel.org> wrote: >>>>> >>>>> + /* >>>>> + * If fl_blocker is NULL, it won't be set again as this >>>>> thread "owns" >>>>> + * the lock and is the only one that might try to claim the >>>>> lock. >>>>> + * Because fl_blocker is explicitly set last during a delete, >>>>> it's >>>>> + * safe to locklessly test to see if it's NULL. If it is, >>>>> then we know >>>>> + * that no new locks can be inserted into its >>>>> fl_blocked_requests list, >>>>> + * and we can therefore avoid doing anything further as long >>>>> as that >>>>> + * list is empty. >>>>> + */ >>>>> + if (!smp_load_acquire(&waiter->fl_blocker) && >>>>> + list_empty(&waiter->fl_blocked_requests)) >>>>> + return status; >>>> >>>> Ack. This looks sane to me now. >>>> >>>> yangerkun - how did you find the original problem?\ >>> >>> While try to fix CVE-2019-19769, add some log in __locks_wake_up_blocks >>> help me to rebuild the problem soon. This help me to discern the problem >>> soon. >>> >>>> Would you mind using whatever stress test that caused commit >>>> 6d390e4b5d48 ("locks: fix a potential use-after-free problem when >>>> wakeup a waiter") with this patch? And if you did it analytically, >>>> you're a champ and should look at this patch too! >>> >>> I will try to understand this patch, and if it's looks good to me, will >>> do the performance test! >> >> This patch looks good to me, with this patch, the bug '6d390e4b5d48 >> ("locks: fix a potential use-after-free problem when wakeup a waiter")' >> describes won't happen again. Actually, I find that syzkaller has report >> this bug before[1], and the log of it can help us to reproduce it with >> some latency in __locks_wake_up_blocks! >> >> Also, some ltp testcases describes in [2] pass too with the patch! >> >> For performance test, I have try to understand will-it-scale/lkp, but it >> seem a little complex to me, and may need some more time. So, Rong Chen, >> can you help to do this? Or the results may come a little later... >> >> Thanks, >> ---- >> [1] https://syzkaller.appspot.com/bug?extid=922689db06e57b69c240 >> [2] https://lkml.org/lkml/2020/3/11/578 > > Thanks yangerkun. Let me know if you want to add your Reviewed-by tag.
Yeah, you can add:
Reviewed-by: yangerkun <yangerkun@huawei.com>
> > Cheers, >
| |