From: yangerkun <yangerkun@huawei.com>
To: Jeff Layton <jlayton@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Cc: NeilBrown <neilb@suse.de>,
kernel test robot <rong.a.chen@intel.com>,
LKML <linux-kernel@vger.kernel.org>, <lkp@lists.01.org>,
Bruce Fields <bfields@fieldses.org>,
Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [locks] 6d390e4b5d: will-it-scale.per_process_ops -96.6% regression
Date: Wed, 18 Mar 2020 09:09:13 +0800 [thread overview]
Message-ID: <79d65a56-5281-502f-8d8f-568e082cacf4@huawei.com> (raw)
In-Reply-To: <61d6b91e9387969f5dfaba192aee366cc9b310f0.camel@kernel.org>
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,
>
next prev parent reply other threads:[~2020-03-18 1:09 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-08 14:03 [locks] 6d390e4b5d: will-it-scale.per_process_ops -96.6% regression kernel test robot
2020-03-09 14:36 ` Jeff Layton
2020-03-09 15:52 ` Linus Torvalds
2020-03-09 17:22 ` Jeff Layton
2020-03-09 19:09 ` Jeff Layton
2020-03-09 19:53 ` Jeff Layton
2020-03-09 21:42 ` NeilBrown
2020-03-09 21:58 ` Jeff Layton
2020-03-10 7:52 ` kernel test robot
2020-03-09 22:11 ` Jeff Layton
2020-03-10 3:24 ` yangerkun
2020-03-10 7:54 ` kernel test robot
2020-03-10 12:52 ` Jeff Layton
2020-03-10 14:18 ` yangerkun
2020-03-10 15:06 ` Jeff Layton
2020-03-10 17:27 ` Jeff Layton
2020-03-10 21:01 ` NeilBrown
2020-03-10 21:14 ` Jeff Layton
2020-03-10 21:21 ` NeilBrown
2020-03-10 21:47 ` Linus Torvalds
2020-03-10 22:07 ` Jeff Layton
2020-03-10 22:31 ` Linus Torvalds
2020-03-11 22:22 ` NeilBrown
2020-03-12 0:38 ` Linus Torvalds
2020-03-12 4:42 ` NeilBrown
2020-03-12 12:31 ` Jeff Layton
2020-03-12 22:19 ` NeilBrown
2020-03-14 1:11 ` Jeff Layton
2020-03-12 16:07 ` Linus Torvalds
2020-03-14 1:31 ` Jeff Layton
2020-03-14 2:31 ` NeilBrown
2020-03-14 15:58 ` Linus Torvalds
2020-03-15 13:54 ` Jeff Layton
2020-03-16 5:06 ` NeilBrown
2020-03-16 11:07 ` Jeff Layton
2020-03-16 17:26 ` Linus Torvalds
2020-03-17 1:41 ` yangerkun
2020-03-17 14:05 ` yangerkun
2020-03-17 16:07 ` Jeff Layton
2020-03-18 1:09 ` yangerkun [this message]
2020-03-19 17:51 ` Jeff Layton
2020-03-19 19:23 ` Linus Torvalds
2020-03-19 19:24 ` Jeff Layton
2020-03-19 19:35 ` Linus Torvalds
2020-03-19 20:10 ` Jeff Layton
2020-03-16 22:45 ` NeilBrown
2020-03-17 15:59 ` Jeff Layton
2020-03-17 21:27 ` NeilBrown
2020-03-18 5:12 ` kernel test robot
2020-03-16 4:26 ` NeilBrown
2020-03-11 1:57 ` yangerkun
2020-03-11 12:52 ` Jeff Layton
2020-03-11 13:26 ` yangerkun
2020-03-11 22:15 ` NeilBrown
2020-03-10 7:50 ` kernel test robot
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