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From:   Eric Dumazet <edumazet@google.com>
Date:   Thu, 12 May 2022 14:19:51 -0700
Message-ID: <CANn89i+XHh1An6fDA0CH1Fb2k_-G8_CCzEmXGKqB4tRAMH9s4w@mail.gmail.com>
Subject: Re: [syzbot] UBSAN: shift-out-of-bounds in tcf_pedit_init
To:     syzbot <syzbot+8ed8fc4c57e9dcf23ca6@syzkaller.appspotmail.com>
Cc:     David Miller <davem@davemloft.net>,
        Jamal Hadi Salim <jhs@mojatatu.com>,
        Jiri Pirko <jiri@resnulli.us>,
        Jakub Kicinski <kuba@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>, Paolo Abeni <pabeni@redhat.com>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Cong Wang <xiyou.wangcong@gmail.com>
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On Thu, May 12, 2022 at 2:18 PM syzbot
<syzbot+8ed8fc4c57e9dcf23ca6@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    810c2f0a3f86 mlxsw: Avoid warning during ip6gre device rem..
> git tree:       net
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=1448a599f00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=331feb185f8828e0
> dashboard link: https://syzkaller.appspot.com/bug?extid=8ed8fc4c57e9dcf23ca6
> 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=104e9749f00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15f913b9f00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+8ed8fc4c57e9dcf23ca6@syzkaller.appspotmail.com
>
> netlink: 28 bytes leftover after parsing attributes in process `syz-executor151'.
> netlink: 28 bytes leftover after parsing attributes in process `syz-executor151'.
> ================================================================================
> UBSAN: shift-out-of-bounds in net/sched/act_pedit.c:238:43
> shift exponent 1400735974 is too large for 32-bit type 'unsigned int'
> CPU: 0 PID: 3606 Comm: syz-executor151 Not tainted 5.18.0-rc5-syzkaller-00165-g810c2f0a3f86 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
>  ubsan_epilogue+0xb/0x50 lib/ubsan.c:151
>  __ubsan_handle_shift_out_of_bounds.cold+0xb1/0x187 lib/ubsan.c:322
>  tcf_pedit_init.cold+0x1a/0x1f net/sched/act_pedit.c:238
>  tcf_action_init_1+0x414/0x690 net/sched/act_api.c:1367
>  tcf_action_init+0x530/0x8d0 net/sched/act_api.c:1432
>  tcf_action_add+0xf9/0x480 net/sched/act_api.c:1956
>  tc_ctl_action+0x346/0x470 net/sched/act_api.c:2015
>  rtnetlink_rcv_msg+0x413/0xb80 net/core/rtnetlink.c:5993
>  netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2502
>  netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
>  netlink_unicast+0x543/0x7f0 net/netlink/af_netlink.c:1345
>  netlink_sendmsg+0x904/0xe00 net/netlink/af_netlink.c:1921
>  sock_sendmsg_nosec net/socket.c:705 [inline]
>  sock_sendmsg+0xcf/0x120 net/socket.c:725
>  ____sys_sendmsg+0x6e2/0x800 net/socket.c:2413
>  ___sys_sendmsg+0xf3/0x170 net/socket.c:2467
>  __sys_sendmsg+0xe5/0x1b0 net/socket.c:2496
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x7fe36e9e1b59
> Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffef796fe88 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fe36e9e1b59
> RDX: 0000000000000000 RSI: 0000000020000300 RDI: 0000000000000003
> RBP: 00007fe36e9a5d00 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007fe36e9a5d90
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>  </TASK>
> ================================================================================
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches

As mentioned earlier, this came with

commit 8b796475fd7882663a870456466a4fb315cc1bd6
Author: Paolo Abeni <pabeni@redhat.com>
Date:   Tue May 10 16:57:34 2022 +0200

    net/sched: act_pedit: really ensure the skb is writable