Message-ID: <CANn89iLwMhOnrmQTZJ+BqZJSbJZ+Q4W6xRknAAr+uSrk5TX-EQ@mail.gmail.com>
Date:   Wed, 13 Sep 2023 10:41:41 +0200
From:   Eric Dumazet <edumazet@...gle.com>
To:     syzbot <syzbot+62cbf263225ae13ff153@...kaller.appspotmail.com>,
        David Howells <dhowells@...hat.com>
Cc:     bpf@...r.kernel.org, davem@...emloft.net, dsahern@...nel.org,
        kuba@...nel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, pabeni@...hat.com,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] WARNING in __ip6_append_data

On Wed, Sep 13, 2023 at 8:19 AM syzbot
<syzbot+62cbf263225ae13ff153@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    65d6e954e378 Merge tag 'gfs2-v6.5-rc5-fixes' of git://git...
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=142177f4680000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=b273cdfbc13e9a4b
> dashboard link: https://syzkaller.appspot.com/bug?extid=62cbf263225ae13ff153
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11f37a0c680000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10034f3fa80000
>

CC David

Warning added in

commit ce650a1663354a6cad7145e7f5131008458b39d4
Author: David Howells <dhowells@...hat.com>
Date:   Wed Aug 2 08:36:50 2023 +0100

    udp6: Fix __ip6_append_data()'s handling of MSG_SPLICE_PAGES


> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/74df7181e630/disk-65d6e954.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/8455d5988dfe/vmlinux-65d6e954.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/8ee7b79f0dfd/bzImage-65d6e954.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+62cbf263225ae13ff153@...kaller.appspotmail.com
>
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 5042 at net/ipv6/ip6_output.c:1800 __ip6_append_data.isra.0+0x1be8/0x47f0 net/ipv6/ip6_output.c:1800
> Modules linked in:
> CPU: 1 PID: 5042 Comm: syz-executor133 Not tainted 6.5.0-syzkaller-11938-g65d6e954e378 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
> RIP: 0010:__ip6_append_data.isra.0+0x1be8/0x47f0 net/ipv6/ip6_output.c:1800
> Code: db f6 ff ff e8 09 d5 97 f8 49 8d 44 24 ff 48 89 44 24 60 49 8d 6c 24 07 e9 c2 f6 ff ff 4c 8b b4 24 90 01 00 00 e8 e8 d4 97 f8 <0f> 0b 48 8b 44 24 10 45 89 f4 48 8d 98 74 02 00 00 e8 d2 d4 97 f8
> RSP: 0018:ffffc90003a1f3b8 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: 0000000000001004 RCX: 0000000000000000
> RDX: ffff88801fe70000 RSI: ffffffff88efcf18 RDI: 0000000000000006
> RBP: 0000000000001000 R08: 0000000000000006 R09: 0000000000001004
> R10: 0000000000001000 R11: 0000000000000000 R12: 0000000000000001
> R13: dffffc0000000000 R14: 0000000000001004 R15: ffff888019f31000
> FS:  0000555557280380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000000045ad50 CR3: 0000000072666000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  ip6_append_data+0x1e6/0x510 net/ipv6/ip6_output.c:1895
>  l2tp_ip6_sendmsg+0xdf9/0x1cc0 net/l2tp/l2tp_ip6.c:631
>  inet_sendmsg+0x9d/0xe0 net/ipv4/af_inet.c:840
>  sock_sendmsg_nosec net/socket.c:730 [inline]
>  sock_sendmsg+0xd9/0x180 net/socket.c:753
>  splice_to_socket+0xade/0x1010 fs/splice.c:881
>  do_splice_from fs/splice.c:933 [inline]
>  direct_splice_actor+0x118/0x180 fs/splice.c:1142
>  splice_direct_to_actor+0x347/0xa30 fs/splice.c:1088
>  do_splice_direct+0x1af/0x280 fs/splice.c:1194
>  do_sendfile+0xb88/0x1390 fs/read_write.c:1254
>  __do_sys_sendfile64 fs/read_write.c:1322 [inline]
>  __se_sys_sendfile64 fs/read_write.c:1308 [inline]
>  __x64_sys_sendfile64+0x1d6/0x220 fs/read_write.c:1308
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7f6b11150469
> Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 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 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fffd14e71a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
> RAX: ffffffffffffffda RBX: 00007fffd14e7378 RCX: 00007f6b11150469
> RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000005
> RBP: 00007f6b111c3610 R08: 00007fffd14e7378 R09: 00007fffd14e7378
> R10: 000000010000a006 R11: 0000000000000246 R12: 0000000000000001
> R13: 00007fffd14e7368 R14: 0000000000000001 R15: 0000000000000001
>  </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@...glegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the bug is already fixed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
>
> If you want to overwrite bug's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the bug is a duplicate of another bug, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup

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