linux-kernel - Re: [syzbot] [net?] WARNING in udp_tunnel_update_gro

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Message-ID: <f2d7e0d6-8dc1-4c1d-bf1a-ea9db7ec554b@redhat.com>
Date: Tue, 18 Mar 2025 18:39:48 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: syzbot <syzbot+8c469a2260132cd095c1@...kaller.appspotmail.com>,
 davem@...emloft.net, dsahern@...nel.org, edumazet@...gle.com,
 horms@...nel.org, kuba@...nel.org, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] WARNING in udp_tunnel_update_gro_rcv

On 3/18/25 5:03 PM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    aedfbe251e1c Merge branch 'udp_tunnel-gro-optimizations'
> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=177f45e4580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=aeeec842a6bdc8b9
> dashboard link: https://syzkaller.appspot.com/bug?extid=8c469a2260132cd095c1
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/18e6408e4123/disk-aedfbe25.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/1cdafe4afee8/vmlinux-aedfbe25.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/eda00f4a96d9/bzImage-aedfbe25.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+8c469a2260132cd095c1@...kaller.appspotmail.com
> 
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 24136 at net/ipv4/udp_offload.c:118 udp_tunnel_update_gro_rcv+0x31d/0x670 net/ipv4/udp_offload.c:118
> Modules linked in:
> CPU: 1 UID: 0 PID: 24136 Comm: syz.0.4789 Not tainted 6.14.0-rc6-syzkaller-01279-gaedfbe251e1c #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
> RIP: 0010:udp_tunnel_update_gro_rcv+0x31d/0x670 net/ipv4/udp_offload.c:118
> Code: 23 48 89 eb e8 14 47 4f f7 c7 05 ca a9 32 10 01 00 00 00 31 ed 45 31 ed e9 80 01 00 00 e8 fb 46 4f f7 eb 40 e8 f4 46 4f f7 90 <0f> 0b 90 e9 5a 02 00 00 e8 e6 46 4f f7 eb 2b e8 df 46 4f f7 eb 24
> RSP: 0018:ffffc9000ad7fc50 EFLAGS: 00010293
> RAX: ffffffff8a72ab0e RBX: 1ffff1100502bb6f RCX: ffff888020f55a00
> RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000004
> RBP: ffffffff86c2d1a0 R08: ffffffff8a72a6eb R09: 1ffffffff207a2ee
> R10: dffffc0000000000 R11: fffffbfff207a2ef R12: dffffc0000000000
> R13: 0000000000000004 R14: ffff88802815db78 R15: 0000000000000000
> FS:  0000555582b32500(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000040000001e030 CR3: 0000000034eca000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  udp_tunnel_cleanup_gro include/net/udp_tunnel.h:220 [inline]
>  udpv6_destroy_sock+0x230/0x2a0 net/ipv6/udp.c:1829
>  sk_common_release+0x71/0x2e0 net/core/sock.c:3892
>  inet_release+0x17d/0x200 net/ipv4/af_inet.c:435
>  __sock_release net/socket.c:647 [inline]
>  sock_close+0xbc/0x240 net/socket.c:1389
>  __fput+0x3e9/0x9f0 fs/file_table.c:464
>  task_work_run+0x24f/0x310 kernel/task_work.c:227
>  resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
>  exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
>  exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
>  __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
>  syscall_exit_to_user_mode+0x13f/0x340 kernel/entry/common.c:218
>  do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f3518f8d169
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffdfbd8d008 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
> RAX: 0000000000000000 RBX: 00007f35191a7ba0 RCX: 00007f3518f8d169
> RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
> RBP: 00007f35191a7ba0 R08: 00000000000000e8 R09: 0000000cfbd8d2ff
> R10: 00000000003ffcf4 R11: 0000000000000246 R12: 00000000000d64d1
> R13: 00007f35191a6160 R14: ffffffffffffffff R15: 00007ffdfbd8d120
>  </TASK>

Whoops, I did not notice that xfrm sets up->gro_receive, too, using a
different code path WRT setup_udp_tunnel_sock().

I think it's better to relax this WARN.

/P