Messages in this thread | | | Subject | Re: [locks] 6d390e4b5d: will-it-scale.per_process_ops -96.6% regression | From | Jeff Layton <> | Date | Tue, 17 Mar 2020 12:07:15 -0400 |
| |
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.
Cheers, -- Jeff Layton <jlayton@kernel.org>
| |