From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Jakub Kicinski <kuba@kernel.org>
Cc: Eric Dumazet <edumazet@google.com>,
syzbot <syzbot+c2775460db0e1c70018e@syzkaller.appspotmail.com>,
netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com,
davem@davemloft.net, linux-kernel@vger.kernel.org,
pabeni@redhat.com, wireguard@lists.zx2c4.com, jann@thejh.net
Subject: Re: [syzbot] [wireguard?] KASAN: slab-use-after-free Write in enqueue_timer
Date: Tue, 23 May 2023 19:01:31 +0200 [thread overview]
Message-ID: <ZGzxa18w-v8Dsy5D@zx2c4.com> (raw)
In-Reply-To: <20230523094736.3a9f6f8c@kernel.org>
On Tue, May 23, 2023 at 09:47:36AM -0700, Jakub Kicinski wrote:
> On Tue, 23 May 2023 18:42:53 +0200 Jason A. Donenfeld wrote:
> > > It should, no idea why it isn't. Looking thru the code now I don't see
> > > any obvious gaps where timer object is on a list but not active :S
> > > There's no way to get a vmcore from syzbot, right? :)
> > >
> > > Also I thought the shutdown leads to a warning when someone tries to
> > > schedule the dead timer but in fact add_timer() just exits cleanly.
> > > So the shutdown won't help us find the culprit :(
> >
> > Worth noting that it could also be caused by adding to a dead timer
> > anywhere in priv_data of another netdev, not just the sole timer_list
> > in net_device.
>
> Oh, I thought you zero'ed in on the watchdog based on offsets.
> Still, object debug should track all timers in the slab and complain
> on the free path.
No, I mentioned watchdog because it's the only timer_list in struct
net_device.
Offset analysis is an interesting idea though. Look at this:
> The buggy address belongs to the object at ffff88801ecc0000
> which belongs to the cache kmalloc-cg-8k of size 8192
> The buggy address is located 5376 bytes inside of
> freed 8192-byte region [ffff88801ecc0000, ffff88801ecc2000)
IDA says that for syzkaller's vmlinux, net_device has a size of 0xc80
and wg_device has a size of 0x880. 0xc80+0x880=5376. Coincidence that
the address offset is just after what wg uses?
Hm.
Jason
next prev parent reply other threads:[~2023-05-23 17:04 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-30 18:01 syzbot
2023-05-23 15:46 ` Jason A. Donenfeld
2023-05-23 16:05 ` Jakub Kicinski
2023-05-23 16:12 ` Eric Dumazet
2023-05-23 16:41 ` Jakub Kicinski
2023-05-23 16:42 ` Jason A. Donenfeld
2023-05-23 16:47 ` Jakub Kicinski
2023-05-23 17:01 ` Jason A. Donenfeld [this message]
2023-05-23 17:05 ` Eric Dumazet
2023-05-23 17:07 ` Eric Dumazet
2023-05-24 8:24 ` Dmitry Vyukov
2023-05-24 15:33 ` Jakub Kicinski
2023-05-24 15:39 ` Jakub Kicinski
2023-05-23 16:14 ` Jason A. Donenfeld
2023-05-23 16:46 ` Jakub Kicinski
2023-05-23 16:47 ` Jason A. Donenfeld
2023-05-23 17:16 ` Jason A. Donenfeld
2023-05-23 17:28 ` Jason A. Donenfeld
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