From: Dmitry Vyukov <dvyukov@google.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Greg KH <greg@kroah.com>, Kees Cook <keescook@chromium.org>,
Alexey Dobriyan <adobriyan@gmail.com>,
security@kernel.org, Akinobu Mita <akinobu.mita@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
syzkaller-bugs@googlegroups.com,
Vegard Nossum <vegard.nossum@oracle.com>
Subject: Re: general protection fault in show_timer
Date: Thu, 14 Dec 2017 15:34:24 +0100 [thread overview]
Message-ID: <CACT4Y+Yu1csMLNa0P=RfEtWC+f0VbnX8Q8L63doWqRJU0c5KLA@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1712141525300.4998@nanos>
On Thu, Dec 14, 2017 at 3:26 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Tue, 12 Dec 2017, Greg KH wrote:
>
>> On Tue, Dec 05, 2017 at 11:58:07AM -0800, Kees Cook wrote:
>> > On Thu, Nov 30, 2017 at 4:57 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
>> > > On Thu, 30 Nov 2017, Alexey Dobriyan wrote:
>> > >
>> > >> [cc security@]
>> > >> 100% oops with interrupts disabled by nobody
>> > >> or kernel memory read
>> > >> [nods]
>> > >> you named the bug already
>> > >>
>> > >> "notify" directly comes from userspace struct sigevent::sigev_notify
>> > >> without adult supervision.
>> > >>
>> > >> Reproducer is timer_create + read(/proc/self/timers)
>> > >
>> > > Bah. That's a really old one.
>> > >
>> > > Tentative fix below. That needs more though but looking at the existing
>> > > check there is only one valid combo with SIGEV_THREAD_ID.
>> > >
>> > > Thanks,
>> > >
>> > > tglx
>> > >
>> > > 8<----------------
>> > > --- a/kernel/time/posix-timers.c
>> > > +++ b/kernel/time/posix-timers.c
>> > > @@ -434,6 +434,16 @@ static struct pid *good_sigevent(sigeven
>> > > {
>> > > struct task_struct *rtn = current->group_leader;
>> > >
>> > > + switch (event->sigev_notify) {
>> > > + case SIGEV_NONE:
>> > > + case SIGEV_SIGNAL:
>> > > + case SIGEV_SIGNAL | SIGEV_THREAD_ID:
>> > > + case SIGEV_THREAD:
>> > > + break;
>> > > + default:
>> > > + return NULL;
>> > > + }
>> > > +
>> > > if ((event->sigev_notify & SIGEV_THREAD_ID ) &&
>> > > (!(rtn = find_task_by_vpid(event->sigev_notify_thread_id)) ||
>> > > !same_thread_group(rtn, current) ||
>> >
>> > FWIW, this looks correct to me.
>>
>> Did this ever go anywhere? I don't see it in Linus's tree yet...
>
> I learned yesterday that syzboz is understuffed and cannot test patches, so
> I need to find a minute to run the reproducer myself and verify that the
> patch is correct.
Hi Thomas,
Why do you say so? Have you tried to ask it to test?
https://github.com/google/syzkaller/blob/master/docs/syzbot.md#communication-with-syzbot
What happened?
next prev parent reply other threads:[~2017-12-14 14:34 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <94eb2c18a77ce8d832055f2cf263@google.com>
2017-11-30 11:08 ` general protection fault in show_timer Alexey Dobriyan
2017-11-30 11:31 ` Dmitry Vyukov
2017-11-30 11:38 ` Dmitry Vyukov
2017-11-30 12:20 ` Alexey Dobriyan
2017-11-30 12:57 ` Dmitry Vyukov
2017-11-30 12:57 ` Thomas Gleixner
2017-12-05 19:58 ` Kees Cook
2017-12-12 8:33 ` Greg KH
2017-12-14 14:26 ` Thomas Gleixner
2017-12-14 14:34 ` Dmitry Vyukov [this message]
2017-12-14 15:34 ` Thomas Gleixner
2017-12-14 18:36 ` Eric Biggers
2017-12-15 16:40 ` Thomas Gleixner
2017-12-19 1:01 ` Eric Biggers
2017-12-04 3:17 ` syzbot
2017-12-04 12:11 ` Thomas Gleixner
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