From: Dmitry Vyukov <dvyukov@google.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
Eric Dumazet <edumazet@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>,
Netdev <netdev@vger.kernel.org>,
syzbot <syzbot+95c862be69e37145543f@syzkaller.appspotmail.com>,
Mark Brown <broonie@kernel.org>,
Kees Cook <keescook@chromium.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
mbenes@suse.cz, syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
Will Deacon <will@kernel.org>, Ard Biesheuvel <ardb@kernel.org>
Subject: Re: KASAN: invalid-access Write in enqueue_timer
Date: Wed, 17 Feb 2021 07:37:06 +0100 [thread overview]
Message-ID: <CACT4Y+bXSn+gh-AbVJmDvLOoG84Za6=bBGaXb=VnQFvosbbG+A@mail.gmail.com> (raw)
In-Reply-To: <CACT4Y+ZH4ViZix7qyPPXtcgaanimm8CmSu1J8qhqpEedxC=fmQ@mail.gmail.com>
On Tue, Feb 16, 2021 at 7:15 PM Dmitry Vyukov <dvyukov@google.com> wrote:
> > On Tue, Feb 16, 2021 at 06:50:20PM +0100, Jason A. Donenfeld wrote:
> > > On Tue, Feb 16, 2021 at 6:46 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
> > > > On Tue, Feb 16, 2021 at 6:28 PM Catalin Marinas <catalin.marinas@arm.com> wrote:
> > > > > > hlist_add_head include/linux/list.h:883 [inline]
> > > > > > enqueue_timer+0x18/0xc0 kernel/time/timer.c:581
> > > > > > mod_timer+0x14/0x20 kernel/time/timer.c:1106
> > > > > > mod_peer_timer drivers/net/wireguard/timers.c:37 [inline]
> > > > > > wg_timers_any_authenticated_packet_traversal+0x68/0x90 drivers/net/wireguard/timers.c:215
> > > >
> > > > The line of hlist_add_head that it's hitting is:
> > > >
> > > > static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
> > > > {
> > > > struct hlist_node *first = h->first;
> > > > WRITE_ONCE(n->next, first);
> > > > if (first)
> > > >
> > > > So that means it's the dereferencing of h that's a problem. That comes from:
> > > >
> > > > static void enqueue_timer(struct timer_base *base, struct timer_list *timer,
> > > > unsigned int idx, unsigned long bucket_expiry)
> > > > {
> > > >
> > > > hlist_add_head(&timer->entry, base->vectors + idx);
> > > >
> > > > That means it concerns base->vectors + idx, not the timer_list object
> > > > that wireguard manages. That's confusing. Could that imply that the
> > > > bug is in freeing a previous timer without removing it from the timer
> > > > lists, so that it winds up being in base->vectors?
> >
> > Good point, it's indeed likely that the timer list is messed up already,
> > just an unlucky encounter in the wireguard code.
> >
> > > Digging around on syzkaller, it looks like there's a similar bug on
> > > jbd2, concerning iptunnels's allocation:
> > >
> > > https://syzkaller.appspot.com/text?tag=CrashReport&x=13afb19cd00000
> > [...]
> > > It might not actually be a wireguard bug?
> >
> > I wonder whether syzbot reported similar issues with
> > CONFIG_KASAN_SW_TAGS. It shouldn't be that different from the HW_TAGS
> > but at least we can rule out qemu bugs with the MTE emulation.
>
> +Eric
I've seen some similar reports on other syzkaller instances. They all
have similar alloc/free stacks, but different access stacks.
This does not seem to be wireguard nor arm/mte related. It seems that
something released the device prematurely, and then some innocent code
gets a use-after-free.
prev parent reply other threads:[~2021-02-17 6:38 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-16 0:06 KASAN: invalid-access Write in enqueue_timer syzbot
2021-02-16 17:28 ` Catalin Marinas
2021-02-16 17:46 ` Jason A. Donenfeld
2021-02-16 17:50 ` Jason A. Donenfeld
2021-02-16 18:01 ` Catalin Marinas
2021-02-16 18:15 ` Dmitry Vyukov
2021-02-17 6:37 ` Dmitry Vyukov [this message]
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