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From:   Eric Dumazet <edumazet@google.com>
Date:   Wed, 5 Jan 2022 05:59:35 -0800
Message-ID: <CANn89i+LbcWn3xoYU-eMjjmQPz0x1pSAat2OpF=i0+RByc-h4w@mail.gmail.com>
Subject: Re: [syzbot] kernel BUG in pskb_expand_head
To:     syzbot <syzbot+4c63f36709a642f801c5@syzkaller.appspotmail.com>
Cc:     anthony.l.nguyen@intel.com, changbin.du@intel.com,
        Christian Brauner <christian.brauner@ubuntu.com>,
        David Miller <davem@davemloft.net>,
        Eric Dumazet <eric.dumazet@gmail.com>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        intel-wired-lan-owner@osuosl.org, intel-wired-lan@lists.osuosl.org,
        Jesse Brandeburg <jesse.brandeburg@intel.com>,
        Jakub Kicinski <kuba@kernel.org>, linux-can@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        Marc Kleine-Budde <mkl@pengutronix.de>,
        netdev <netdev@vger.kernel.org>,
        Oliver Hartkopp <socketcan@hartkopp.net>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Yajun Deng <yajun.deng@linux.dev>
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On Wed, Jan 5, 2022 at 3:20 AM syzbot
<syzbot+4c63f36709a642f801c5@syzkaller.appspotmail.com> wrote:
>
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit:    c9e6606c7fe9 Linux 5.16-rc8
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=148351c3b00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=32f9fa260d7413b4
> dashboard link: https://syzkaller.appspot.com/bug?extid=4c63f36709a642f801c5
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15435e2bb00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12f4508db00000
>

This C repro looks legit, bug should be in CAN layer.

> The issue was bisected to:
>
> commit e4b8954074f6d0db01c8c97d338a67f9389c042f
> Author: Eric Dumazet <edumazet@google.com>
> Date:   Tue Dec 7 01:30:37 2021 +0000
>
>     netlink: add net device refcount tracker to struct ethnl_req_info

Ignore this bisection, an unrelated commit whent in its way.

>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=109e6fcbb00000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=129e6fcbb00000
> console output: https://syzkaller.appspot.com/x/log.txt?x=149e6fcbb00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+4c63f36709a642f801c5@syzkaller.appspotmail.com
> Fixes: e4b8954074f6 ("netlink: add net device refcount tracker to struct ethnl_req_info")
>
> skbuff: skb_over_panic: text:ffffffff88235fb8 len:4096 put:4096 head:ffff888021cb8400 data:ffff888021cb8400 tail:0x1000 end:0xc0 dev:<NULL>
> ------------[ cut here ]------------
> kernel BUG at net/core/skbuff.c:113!
> invalid opcode: 0000 [#1] PREEMPT SMP KASAN
> CPU: 1 PID: 19 Comm: ksoftirqd/1 Not tainted 5.16.0-rc8-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:skb_panic+0x16c/0x16e net/core/skbuff.c:113
> Code: f8 4c 8b 4c 24 10 8b 4b 70 41 56 45 89 e8 4c 89 e2 41 57 48 89 ee 48 c7 c7 e0 4b ad 8a ff 74 24 10 ff 74 24 20 e8 6e 24 c2 ff <0f> 0b e8 74 92 38 f8 4c 8b 64 24 18 e8 da 47 7f f8 48 c7 c1 80 58
> RSP: 0018:ffffc90000d979e0 EFLAGS: 00010286
> RAX: 000000000000008b RBX: ffff888021ccb500 RCX: 0000000000000000
> RDX: ffff88801196d700 RSI: ffffffff815f0948 RDI: fffff520001b2f2e
> RBP: ffffffff8aad58c0 R08: 000000000000008b R09: 0000000000000000
> R10: ffffffff815ea6ee R11: 0000000000000000 R12: ffffffff88235fb8
> R13: 0000000000001000 R14: ffffffff8aad4ba0 R15: 00000000000000c0
> FS:  0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f886c8cc718 CR3: 000000007ad6d000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  skb_over_panic net/core/skbuff.c:118 [inline]
>  skb_put.cold+0x24/0x24 net/core/skbuff.c:1990
>  isotp_rcv_cf net/can/isotp.c:570 [inline]
>  isotp_rcv+0xa38/0x1e30 net/can/isotp.c:668
>  deliver net/can/af_can.c:574 [inline]
>  can_rcv_filter+0x445/0x8d0 net/can/af_can.c:635
>  can_receive+0x31d/0x580 net/can/af_can.c:665
>  can_rcv+0x120/0x1c0 net/can/af_can.c:696
>  __netif_receive_skb_one_core+0x114/0x180 net/core/dev.c:5465
>  __netif_receive_skb+0x24/0x1b0 net/core/dev.c:5579
>  process_backlog+0x2a5/0x6c0 net/core/dev.c:6455
>  __napi_poll+0xaf/0x440 net/core/dev.c:7023
>  napi_poll net/core/dev.c:7090 [inline]
>  net_rx_action+0x801/0xb40 net/core/dev.c:7177
>  __do_softirq+0x29b/0x9c2 kernel/softirq.c:558
>  run_ksoftirqd kernel/softirq.c:921 [inline]
>  run_ksoftirqd+0x2d/0x60 kernel/softirq.c:913
>  smpboot_thread_fn+0x645/0x9c0 kernel/smpboot.c:164
>  kthread+0x405/0x4f0 kernel/kthread.c:327
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
>  </TASK>
> Modules linked in:
> ---[ end trace 9f06028ec4daf4be ]---
> RIP: 0010:skb_panic+0x16c/0x16e net/core/skbuff.c:113
> Code: f8 4c 8b 4c 24 10 8b 4b 70 41 56 45 89 e8 4c 89 e2 41 57 48 89 ee 48 c7 c7 e0 4b ad 8a ff 74 24 10 ff 74 24 20 e8 6e 24 c2 ff <0f> 0b e8 74 92 38 f8 4c 8b 64 24 18 e8 da 47 7f f8 48 c7 c1 80 58
> RSP: 0018:ffffc90000d979e0 EFLAGS: 00010286
> RAX: 000000000000008b RBX: ffff888021ccb500 RCX: 0000000000000000
> RDX: ffff88801196d700 RSI: ffffffff815f0948 RDI: fffff520001b2f2e
> RBP: ffffffff8aad58c0 R08: 000000000000008b R09: 0000000000000000
> R10: ffffffff815ea6ee R11: 0000000000000000 R12: ffffffff88235fb8
> R13: 0000000000001000 R14: ffffffff8aad4ba0 R15: 00000000000000c0
> FS:  0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f886c8cc718 CR3: 000000007ad6d000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>