From: Catalin Marinas <catalin.marinas@arm.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Jan Kara <jack@suse.cz>,
syzbot <syzbot+dec34b033b3479b9ef13@syzkaller.appspotmail.com>,
Amir Goldstein <amir73il@gmail.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
syzkaller <syzkaller@googlegroups.com>
Subject: Re: memory leak in inotify_update_watch
Date: Wed, 8 Jul 2020 12:08:15 +0100 [thread overview]
Message-ID: <20200708110814.GA6308@gaia> (raw)
In-Reply-To: <CACT4Y+ZLx3wT3uvsMr9EOQ35wF+tw3SN_kzgwn2B+K5dTtHrOg@mail.gmail.com>
On Wed, Jul 08, 2020 at 09:17:37AM +0200, Dmitry Vyukov wrote:
> On Tue, Jul 7, 2020 at 8:17 PM Catalin Marinas <catalin.marinas@arm.com> wrote:
> > Kmemleak never performs well under heavy load. Normally you'd need to
> > let the system settle for a bit before checking whether the leaks are
> > still reported. The issue is caused by the memory scanning not stopping
> > the whole machine, so pointers may be hidden in registers on different
> > CPUs (list insertion/deletion for example causes transient kmemleak
> > confusion).
> >
> > I think the syzkaller guys tried a year or so ago to run it in parallel
> > with kmemleak and gave up shortly. The proposal was to add a "stopscan"
> > command to kmemleak which would do this under stop_machine(). However,
> > no-one got to implementing it.
> >
> > So, in this case, does the leak still appear with the reproducer, once
> > the system went idle?
>
> This report came from syzbot, so obviously we did not give up :)
That's good to know ;).
> We don't run scanning in parallel with fuzzing and do a very intricate
> multi-step dance to overcome false positives:
> https://github.com/google/syzkaller/blob/5962a2dc88f6511b77100acdf687c1088f253f6b/executor/common_linux.h#L3407-L3478
> and only report leaks that are reproducible.
> So far I have not seen any noticable amount of false positives, and
> you can see 70 already fixed leaks here:
> https://syzkaller.appspot.com/upstream/fixed?manager=ci-upstream-gce-leak
> https://syzkaller.appspot.com/upstream?manager=ci-upstream-gce-leak
Thanks for the information and the good work here. If you have time, you
could implement the stop_machine() kmemleak scan as well ;).
--
Catalin
next prev parent reply other threads:[~2020-07-08 11:08 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-06 15:42 memory leak in inotify_update_watch syzbot
2020-07-07 15:24 ` Jan Kara
2020-07-07 18:17 ` Catalin Marinas
2020-07-08 7:17 ` Dmitry Vyukov
2020-07-08 11:08 ` Catalin Marinas [this message]
2020-07-08 11:15 ` Dmitry Vyukov
2020-07-08 12:03 ` Catalin Marinas
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