From: Michal Hocko <mhocko@suse.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: syzbot <syzbot+bc9e2d2dbcb347dd215a@syzkaller.appspotmail.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
syzkaller-bugs@googlegroups.com, mptcp@lists.linux.dev,
netdev@vger.kernel.org
Subject: Re: [syzbot] WARNING in page_counter_cancel (3)
Date: Wed, 29 Dec 2021 10:23:07 +0100 [thread overview]
Message-ID: <Ycwo+++dToWQ1RMR@dhcp22.suse.cz> (raw)
In-Reply-To: <20211221155736.90bbc5928bcd779e76ca8f95@linux-foundation.org>
On Tue 21-12-21 15:57:36, Andrew Morton wrote:
> On Sat, 18 Dec 2021 06:04:22 -0800 syzbot <syzbot+bc9e2d2dbcb347dd215a@syzkaller.appspotmail.com> wrote:
>
> > syzbot has found a reproducer for the following issue on:
> >
> > HEAD commit: fbf252e09678 Add linux-next specific files for 20211216
> > git tree: linux-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=1797de99b00000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=7fcbb9aa19a433c8
> > dashboard link: https://syzkaller.appspot.com/bug?extid=bc9e2d2dbcb347dd215a
> > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=135d179db00000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=113edb6db00000
>
> Useful to have that, thanks.
>
> I'm suspecting that mptcp is doing something strange.
Yes.
> Could I as the
> developers to please take a look?
>
>
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+bc9e2d2dbcb347dd215a@syzkaller.appspotmail.com
> >
> > R13: 00007ffdeb858640 R14: 00007ffdeb858680 R15: 0000000000000004
> > </TASK>
> > ------------[ cut here ]------------
> > page_counter underflow: -4294966651 nr_pages=4294967295
__mptcp_mem_reclaim_partial is trying to uncharge (via
__sk_mem_reduce_allocated) negative amount. nr_pages has overflown when
converted from int to unsigned int (-1). I would say that
__mptcp_mem_reclaim_partial has evaluated
reclaimable = mptcp_sk(sk)->rmem_fwd_alloc - sk_unused_reserved_mem(sk)
to 0 and __mptcp_rmem_reclaim(sk, reclaimable - 1) made it -1.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-12-29 9:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-21 12:49 syzbot
2021-12-18 14:04 ` syzbot
2021-12-21 23:57 ` Andrew Morton
2021-12-29 9:23 ` Michal Hocko [this message]
2022-01-05 0:08 ` Mat Martineau
2021-12-18 19:59 ` syzbot
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