From: Jann Horn <[email protected]>
To: Jens Axboe <[email protected]>, "Paul E . McKenney" <[email protected]>
Cc: Dmitry Vyukov <[email protected]>,
syzbot <[email protected]>,
Al Viro <[email protected]>,
io-uring <[email protected]>,
linux-fsdevel <[email protected]>,
Borislav Petkov <[email protected]>, "H. Peter Anvin" <[email protected]>,
LKML <[email protected]>,
Ingo Molnar <[email protected]>,
Peter Zijlstra <[email protected]>,
syzkaller-bugs <[email protected]>,
Thomas Gleixner <[email protected]>,
[email protected], "the arch/x86 maintainers" <[email protected]>,
Dan Carpenter <[email protected]>
Subject: Re: KASAN: use-after-free Read in percpu_ref_switch_to_atomic_rcu
Date: Fri, 6 Mar 2020 15:57:57 +0100 [thread overview]
Message-ID: <CAG48ez3DUAraFL1+agBX=1JVxzh_e2GR=UpX5JUaoyi+1gQ=6w@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
+paulmck
On Wed, Mar 4, 2020 at 3:40 PM Jens Axboe <[email protected]> wrote:
> On 3/4/20 12:59 AM, Dmitry Vyukov wrote:
> > On Fri, Feb 7, 2020 at 9:14 AM syzbot
> > <[email protected]> wrote:
> >>
> >> Hello,
> >>
> >> syzbot found the following crash on:
> >>
> >> HEAD commit: 4c7d00cc Merge tag 'pwm/for-5.6-rc1' of git://git.kernel.o..
> >> git tree: upstream
> >> console output: https://syzkaller.appspot.com/x/log.txt?x=12fec785e00000
> >> kernel config: https://syzkaller.appspot.com/x/.config?x=e162021ddededa72
> >> dashboard link: https://syzkaller.appspot.com/bug?extid=e017e49c39ab484ac87a
> >> compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
> >>
> >> Unfortunately, I don't have any reproducer for this crash yet.
> >>
> >> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> >> Reported-by: [email protected]
> >
> > +io_uring maintainers
> >
> > Here is a repro:
> > https://gist.githubusercontent.com/dvyukov/6b340beab6483a036f4186e7378882ce/raw/cd1922185516453c201df8eded1d4b006a6d6a3a/gistfile1.txt
>
> I've queued up a fix for this:
>
> https://git.kernel.dk/cgit/linux-block/commit/?h=io_uring-5.6&id=9875fe3dc4b8cff1f1b440fb925054a5124403c3
I believe that this fix relies on call_rcu() having FIFO ordering; but
<https://www.kernel.org/doc/Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.html#Callback%20Registry>
says:
| call_rcu() normally acts only on CPU-local state[...] It simply
enqueues the rcu_head structure on a per-CPU list,
Is this fix really correct?
next prev parent reply other threads:[~2020-03-06 14:58 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <[email protected]>
2020-03-04 7:59 ` KASAN: use-after-free Read in percpu_ref_switch_to_atomic_rcu Dmitry Vyukov
2020-03-04 14:40 ` Jens Axboe
2020-03-06 14:35 ` Dan Carpenter
2020-03-06 14:57 ` Jens Axboe
2020-03-06 14:57 ` Jann Horn [this message]
2020-03-06 15:34 ` Jens Axboe
2020-03-06 15:36 ` Jann Horn
2020-03-06 16:44 ` Paul E. McKenney
2020-03-06 17:00 ` Jens Axboe
2020-03-06 17:08 ` Jens Axboe
2020-03-06 17:19 ` Paul E. McKenney
2020-03-06 17:21 ` Jens Axboe
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