Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone

From: David Ahern <dsa@cumulusnetworks.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
	Mahesh Bandewar <maheshb@google.com>,
	Eric Dumazet <edumazet@google.com>,
	David Miller <davem@davemloft.net>,
	Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
	James Morris <jmorris@namei.org>,
	Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
	Patrick McHardy <kaber@trash.net>,
	netdev <netdev@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Cong Wang <xiyou.wangcong@gmail.com>,
	syzkaller <syzkaller@googlegroups.com>
Subject: Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone
Date: Tue, 7 Mar 2017 11:03:39 -0700	[thread overview]
Message-ID: <2b60b1b8-4766-0e36-f6fb-79914bf1925d@cumulusnetworks.com> (raw)
In-Reply-To: <CACT4Y+aDzAYs9mbNGeFEkYSB2wTwomZTGEKn4hDH0PAb4uiLqw@mail.gmail.com>

On 3/7/17 2:21 AM, Dmitry Vyukov wrote:
> I've commented that warning just to see I can obtain more information.
> Then I also got this:
> 
> ------------[ cut here ]------------
> WARNING: CPU: 2 PID: 3990 at net/ipv6/ip6_fib.c:991
> fib6_add+0x2e12/0x3290 net/ipv6/ip6_fib.c:991 net/ipv6/ip6_fib.c:991
> Kernel panic - not syncing: panic_on_warn set ...

again panic_on_warn is triggering ...

> 
> CPU: 2 PID: 3990 Comm: kworker/2:4 Not tainted 4.11.0-rc1+ #311
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> Workqueue: ipv6_addrconf addrconf_dad_work
> Call Trace:
>  __dump_stack lib/dump_stack.c:16 [inline]
>  __dump_stack lib/dump_stack.c:16 [inline] lib/dump_stack.c:52
>  dump_stack+0x2fb/0x3fd lib/dump_stack.c:52 lib/dump_stack.c:52
>  panic+0x20f/0x426 kernel/panic.c:180 kernel/panic.c:180
>  __warn+0x1c4/0x1e0 kernel/panic.c:541 kernel/panic.c:541
>  warn_slowpath_null+0x2c/0x40 kernel/panic.c:584 kernel/panic.c:584
>  fib6_add+0x2e12/0x3290 net/ipv6/ip6_fib.c:991 net/ipv6/ip6_fib.c:991

on this warning:

/* dst.next really should not be set at this point */
if (rt->dst.next && rt->dst.next->ops->family != AF_INET6) {
        pr_warn("fib6_add: adding rt with bad next -- family %d dst
flags %x\n",
                rt->dst.next->ops->family, rt->dst.next->flags);

        WARN_ON(1);
}

You should have seen the pr_warn in the log preceding the WARN_ON dump.

>  __ip6_ins_rt+0x60/0x80 net/ipv6/route.c:948 net/ipv6/route.c:948
>  ip6_ins_rt+0x19b/0x220 net/ipv6/route.c:959 net/ipv6/route.c:959
>  __ipv6_ifa_notify+0x62e/0x7a0 net/ipv6/addrconf.c:5485 net/ipv6/addrconf.c:5485
>  ipv6_ifa_notify+0xdf/0x1d0 net/ipv6/addrconf.c:5518 net/ipv6/addrconf.c:5518
>  addrconf_dad_completed+0xe6/0x950 net/ipv6/addrconf.c:3983
> net/ipv6/addrconf.c:3983
>  addrconf_dad_begin net/ipv6/addrconf.c:3797 [inline]
>  addrconf_dad_begin net/ipv6/addrconf.c:3797 [inline] net/ipv6/addrconf.c:3897
>  addrconf_dad_work+0x32a/0xea0 net/ipv6/addrconf.c:3897 net/ipv6/addrconf.c:3897
>  process_one_work+0xc06/0x1c40 kernel/workqueue.c:2096 kernel/workqueue.c:2096
>  worker_thread+0x223/0x19f0 kernel/workqueue.c:2230 kernel/workqueue.c:2230
>  kthread+0x334/0x400 kernel/kthread.c:229 kernel/kthread.c:229
>  ret_from_fork+0x31/0x40 arch/x86/entry/entry_64.S:430
> arch/x86/entry/entry_64.S:430
> 
> 
> 
> And this without any preceding warnings:
> 
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in fib6_age+0x3fd/0x480
> net/ipv6/ip6_fib.c:1787 at addr ffff88004d4fbe54

another ipv4 route in ipv6 fib walk