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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Sun, 18 Aug 2019 07:13:22 -0700
Message-ID: <CACT4Y+aNTHtbw1upruHtfrLZnUyKkZHU5_3fndmVV6D_zzJJbQ@mail.gmail.com>
Subject: Re: kernel BUG at include/linux/skbuff.h:LINE! (2)
To:     Xin Long <lucien.xin@gmail.com>
Cc:     syzbot <syzbot+eb349eeee854e389c36d@syzkaller.appspotmail.com>,
        davem <davem@davemloft.net>, LKML <linux-kernel@vger.kernel.org>,
        linux-sctp@vger.kernel.org,
        Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>,
        network dev <netdev@vger.kernel.org>,
        Neil Horman <nhorman@tuxdriver.com>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Vlad Yasevich <vyasevich@gmail.com>
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On Sun, Aug 18, 2019 at 7:07 AM Xin Long <lucien.xin@gmail.com> wrote:
>
> On Sat, Aug 17, 2019 at 2:38 AM syzbot
> <syzbot+eb349eeee854e389c36d@syzkaller.appspotmail.com> wrote:
> >
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit:    459c5fb4 Merge branch 'mscc-PTP-support'
> > git tree:       net-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=13f2d33c600000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=d4cf1ffb87d590d7
> > dashboard link: https://syzkaller.appspot.com/bug?extid=eb349eeee854e389c36d
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=111849e2600000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1442c25a600000
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+eb349eeee854e389c36d@syzkaller.appspotmail.com
> >
> > ------------[ cut here ]------------
> > kernel BUG at include/linux/skbuff.h:2225!
> > invalid opcode: 0000 [#1] PREEMPT SMP KASAN
> > CPU: 0 PID: 9030 Comm: syz-executor649 Not tainted 5.3.0-rc3+ #134
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > RIP: 0010:__skb_pull include/linux/skbuff.h:2225 [inline]
> > RIP: 0010:__skb_pull include/linux/skbuff.h:2222 [inline]
> > RIP: 0010:skb_pull_inline include/linux/skbuff.h:2231 [inline]
> > RIP: 0010:skb_pull+0xea/0x110 net/core/skbuff.c:1902
> > Code: 9d c8 00 00 00 49 89 dc 49 89 9d c8 00 00 00 e8 9c e5 dd fb 4c 89 e0
> > 5b 41 5c 41 5d 41 5e 5d c3 45 31 e4 eb ea e8 86 e5 dd fb <0f> 0b e8 df 13
> > 18 fc e9 44 ff ff ff e8 d5 13 18 fc eb 8a e8 ee 13
> > RSP: 0018:ffff88808ac96e10 EFLAGS: 00010293
> > RAX: ffff88809c546000 RBX: 0000000000000004 RCX: ffffffff8594a3a6
> > RDX: 0000000000000000 RSI: ffffffff8594a3fa RDI: 0000000000000004
> > RBP: ffff88808ac96e30 R08: ffff88809c546000 R09: fffffbfff14a8f4f
> > R10: fffffbfff14a8f4e R11: ffffffff8a547a77 R12: 0000000095e28bcc
> > R13: ffff88808ac97478 R14: 00000000ffff8880 R15: ffff88808ac97478
> > FS:  0000555556549880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000000020000100 CR3: 0000000089c3c000 CR4: 00000000001406f0
> > Call Trace:
> >   sctp_inq_pop+0x2f1/0xd80 net/sctp/inqueue.c:202
> >   sctp_endpoint_bh_rcv+0x184/0x8d0 net/sctp/endpointola.c:385
> >   sctp_inq_push+0x1e4/0x280 net/sctp/inqueue.c:80
> >   sctp_rcv+0x2807/0x3590 net/sctp/input.c:256
> >   sctp6_rcv+0x17/0x30 net/sctp/ipv6.c:1049
> >   ip6_protocol_deliver_rcu+0x2fe/0x1660 net/ipv6/ip6_input.c:397
> >   ip6_input_finish+0x84/0x170 net/ipv6/ip6_input.c:438
> >   NF_HOOK include/linux/netfilter.h:305 [inline]
> >   NF_HOOK include/linux/netfilter.h:299 [inline]
> >   ip6_input+0xe4/0x3f0 net/ipv6/ip6_input.c:447
> >   dst_input include/net/dst.h:442 [inline]
> >   ip6_sublist_rcv_finish+0x98/0x1e0 net/ipv6/ip6_input.c:84
> Looks skb_list_del_init() should be called in ip6_sublist_rcv_finish,
> as does in ip_sublist_rcv_finish().

This was recently introduced, right? Only in net-next and linux-next.
Otherwise, is it a remote DoS? If so and if it's present in any
releases, may need a CVE.