* [moderation/CI] Re: BIG TCP for UDP tunnels
@ 2026-02-27 17:19 syzbot ci
2026-02-27 18:15 ` Aleksandr Nogikh
0 siblings, 1 reply; 2+ messages in thread
From: syzbot ci @ 2026-02-27 17:19 UTC (permalink / raw)
To: syzkaller-upstream-moderation; +Cc: syzbot
syzbot ci has tested the following series
[v2] BIG TCP for UDP tunnels
https://lore.kernel.org/all/20260226201600.222044-1-alice.kernel@fastmail.im
* [PATCH net-next v2 01/12] net/sched: act_csum: don't mangle UDP tunnel GSO packets
* [PATCH net-next v2 02/12] udp: gso: Simplify handling length in GSO_PARTIAL
* [PATCH net-next v2 03/12] geneve: Fix off-by-one comparing with GRO_LEGACY_MAX_SIZE
* [PATCH net-next v2 04/12] net: Use helpers to get/set UDP len tree-wide
* [PATCH net-next v2 05/12] net: Enable BIG TCP with partial GSO
* [PATCH net-next v2 06/12] udp: Support gro_ipv4_max_size > 65536
* [PATCH net-next v2 07/12] udp: Support BIG TCP GSO packets where they can occur
* [PATCH net-next v2 08/12] udp: Validate UDP length in udp_gro_receive
* [PATCH net-next v2 09/12] udp: Set length in UDP header to 0 for big GSO packets
* [PATCH net-next v2 10/12] vxlan: Enable BIG TCP packets
* [PATCH net-next v2 11/12] geneve: Enable BIG TCP packets
* [PATCH net-next v2 12/12] selftests: net: Add a test for BIG TCP in UDP tunnels
and found the following issue:
WARNING in l2tp_xmit_skb
Full report is available here:
https://ci.syzbot.org/series/8de1e666-84bd-4f74-b980-539c4b651492
***
WARNING in l2tp_xmit_skb
tree: net-next
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net-next.git
base: fd6dad4e1ae296b67b87291256878a58dad36c93
arch: amd64
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config: https://ci.syzbot.org/builds/f58ab8e4-fdf3-4b35-8063-129b877f1ed8/config
C repro: https://ci.syzbot.org/findings/a09a9cb9-7ad3-49ee-8662-3581bd42cd46/c_repro
syz repro: https://ci.syzbot.org/findings/a09a9cb9-7ad3-49ee-8662-3581bd42cd46/syz_repro
------------[ cut here ]------------
len >= 65536u
WARNING: ./include/linux/udp.h:38 at udp_set_len_short include/linux/udp.h:38 [inline], CPU#1: syz.0.17/5957
WARNING: ./include/linux/udp.h:38 at l2tp_xmit_core net/l2tp/l2tp_core.c:1293 [inline], CPU#1: syz.0.17/5957
WARNING: ./include/linux/udp.h:38 at l2tp_xmit_skb+0x1204/0x18d0 net/l2tp/l2tp_core.c:1327, CPU#1: syz.0.17/5957
Modules linked in:
CPU: 1 UID: 0 PID: 5957 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:udp_set_len_short include/linux/udp.h:38 [inline]
RIP: 0010:l2tp_xmit_core net/l2tp/l2tp_core.c:1293 [inline]
RIP: 0010:l2tp_xmit_skb+0x1204/0x18d0 net/l2tp/l2tp_core.c:1327
Code: 0f 0b 90 e9 21 f9 ff ff e8 e9 05 ec f6 90 0f 0b 90 e9 8d f9 ff ff e8 db 05 ec f6 90 0f 0b 90 e9 cc f9 ff ff e8 cd 05 ec f6 90 <0f> 0b 90 e9 de fa ff ff 44 89 f1 80 e1 07 80 c1 03 38 c1 0f 8c 4f
RSP: 0018:ffffc90003d67878 EFLAGS: 00010293
RAX: ffffffff8ad985e3 RBX: ffff8881a6400090 RCX: ffff8881697f0000
RDX: 0000000000000000 RSI: 0000000000034010 RDI: 000000000000ffff
RBP: dffffc0000000000 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff520007acf00 R12: ffff8881baf20900
R13: 0000000000034010 R14: ffff8881a640008e R15: ffff8881760f7000
FS: 000055557e81f500(0000) GS:ffff8882a9467000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000033000 CR3: 00000001612f4000 CR4: 00000000000006f0
Call Trace:
<TASK>
pppol2tp_sendmsg+0x40a/0x5f0 net/l2tp/l2tp_ppp.c:302
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg net/socket.c:742 [inline]
sock_write_iter+0x503/0x550 net/socket.c:1195
do_iter_readv_writev+0x619/0x8c0 fs/read_write.c:-1
vfs_writev+0x33c/0x990 fs/read_write.c:1059
do_writev+0x154/0x2e0 fs/read_write.c:1105
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f636479c629
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffffd4241c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007f6364a15fa0 RCX: 00007f636479c629
RDX: 0000000000000001 RSI: 0000200000000080 RDI: 0000000000000003
RBP: 00007f6364832b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6364a15fac R14: 00007f6364a15fa0 R15: 00007f6364a15fa0
</TASK>
***
If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
Tested-by: syzbot@syzkaller.appspotmail.com
---
This report is generated by a bot. It may contain errors.
syzbot ci engineers can be reached at syzkaller@googlegroups.com.
The email will later be sent to:
[alice.kernel@fastmail.im alice@isovalent.com andrew@lunn.ch daniel@iogearbox.net davem@davemloft.net dsahern@kernel.org edumazet@google.com fw@strlen.de gal@nvidia.com horms@kernel.org kuba@kernel.org lucien.xin@gmail.com netdev@vger.kernel.org pabeni@redhat.com razor@blackwall.org shuah@kernel.org stfomichev@gmail.com willemdebruijn.kernel@gmail.com]
If the report looks fine to you, reply with:
#syz upstream
If the report is a false positive, reply with
#syz invalid
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [moderation/CI] Re: BIG TCP for UDP tunnels
2026-02-27 17:19 [moderation/CI] Re: BIG TCP for UDP tunnels syzbot ci
@ 2026-02-27 18:15 ` Aleksandr Nogikh
0 siblings, 0 replies; 2+ messages in thread
From: Aleksandr Nogikh @ 2026-02-27 18:15 UTC (permalink / raw)
To: syzbot ci; +Cc: syzkaller-upstream-moderation, syzbot
#syz upstream
On Fri, Feb 27, 2026 at 6:20 PM syzbot ci
<syzbot+ci60beb959ea6a7a80@syzkaller.appspotmail.com> wrote:
>
> syzbot ci has tested the following series
>
> [v2] BIG TCP for UDP tunnels
> https://lore.kernel.org/all/20260226201600.222044-1-alice.kernel@fastmail.im
> * [PATCH net-next v2 01/12] net/sched: act_csum: don't mangle UDP tunnel GSO packets
> * [PATCH net-next v2 02/12] udp: gso: Simplify handling length in GSO_PARTIAL
> * [PATCH net-next v2 03/12] geneve: Fix off-by-one comparing with GRO_LEGACY_MAX_SIZE
> * [PATCH net-next v2 04/12] net: Use helpers to get/set UDP len tree-wide
> * [PATCH net-next v2 05/12] net: Enable BIG TCP with partial GSO
> * [PATCH net-next v2 06/12] udp: Support gro_ipv4_max_size > 65536
> * [PATCH net-next v2 07/12] udp: Support BIG TCP GSO packets where they can occur
> * [PATCH net-next v2 08/12] udp: Validate UDP length in udp_gro_receive
> * [PATCH net-next v2 09/12] udp: Set length in UDP header to 0 for big GSO packets
> * [PATCH net-next v2 10/12] vxlan: Enable BIG TCP packets
> * [PATCH net-next v2 11/12] geneve: Enable BIG TCP packets
> * [PATCH net-next v2 12/12] selftests: net: Add a test for BIG TCP in UDP tunnels
>
> and found the following issue:
> WARNING in l2tp_xmit_skb
>
> Full report is available here:
> https://ci.syzbot.org/series/8de1e666-84bd-4f74-b980-539c4b651492
>
> ***
>
> WARNING in l2tp_xmit_skb
>
> tree: net-next
> URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net-next.git
> base: fd6dad4e1ae296b67b87291256878a58dad36c93
> arch: amd64
> compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
> config: https://ci.syzbot.org/builds/f58ab8e4-fdf3-4b35-8063-129b877f1ed8/config
> C repro: https://ci.syzbot.org/findings/a09a9cb9-7ad3-49ee-8662-3581bd42cd46/c_repro
> syz repro: https://ci.syzbot.org/findings/a09a9cb9-7ad3-49ee-8662-3581bd42cd46/syz_repro
>
> ------------[ cut here ]------------
> len >= 65536u
> WARNING: ./include/linux/udp.h:38 at udp_set_len_short include/linux/udp.h:38 [inline], CPU#1: syz.0.17/5957
> WARNING: ./include/linux/udp.h:38 at l2tp_xmit_core net/l2tp/l2tp_core.c:1293 [inline], CPU#1: syz.0.17/5957
> WARNING: ./include/linux/udp.h:38 at l2tp_xmit_skb+0x1204/0x18d0 net/l2tp/l2tp_core.c:1327, CPU#1: syz.0.17/5957
> Modules linked in:
> CPU: 1 UID: 0 PID: 5957 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> RIP: 0010:udp_set_len_short include/linux/udp.h:38 [inline]
> RIP: 0010:l2tp_xmit_core net/l2tp/l2tp_core.c:1293 [inline]
> RIP: 0010:l2tp_xmit_skb+0x1204/0x18d0 net/l2tp/l2tp_core.c:1327
> Code: 0f 0b 90 e9 21 f9 ff ff e8 e9 05 ec f6 90 0f 0b 90 e9 8d f9 ff ff e8 db 05 ec f6 90 0f 0b 90 e9 cc f9 ff ff e8 cd 05 ec f6 90 <0f> 0b 90 e9 de fa ff ff 44 89 f1 80 e1 07 80 c1 03 38 c1 0f 8c 4f
> RSP: 0018:ffffc90003d67878 EFLAGS: 00010293
> RAX: ffffffff8ad985e3 RBX: ffff8881a6400090 RCX: ffff8881697f0000
> RDX: 0000000000000000 RSI: 0000000000034010 RDI: 000000000000ffff
> RBP: dffffc0000000000 R08: 0000000000000003 R09: 0000000000000004
> R10: dffffc0000000000 R11: fffff520007acf00 R12: ffff8881baf20900
> R13: 0000000000034010 R14: ffff8881a640008e R15: ffff8881760f7000
> FS: 000055557e81f500(0000) GS:ffff8882a9467000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000200000033000 CR3: 00000001612f4000 CR4: 00000000000006f0
> Call Trace:
> <TASK>
> pppol2tp_sendmsg+0x40a/0x5f0 net/l2tp/l2tp_ppp.c:302
> sock_sendmsg_nosec net/socket.c:727 [inline]
> __sock_sendmsg net/socket.c:742 [inline]
> sock_write_iter+0x503/0x550 net/socket.c:1195
> do_iter_readv_writev+0x619/0x8c0 fs/read_write.c:-1
> vfs_writev+0x33c/0x990 fs/read_write.c:1059
> do_writev+0x154/0x2e0 fs/read_write.c:1105
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f636479c629
> Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 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 e8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffffd4241c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
> RAX: ffffffffffffffda RBX: 00007f6364a15fa0 RCX: 00007f636479c629
> RDX: 0000000000000001 RSI: 0000200000000080 RDI: 0000000000000003
> RBP: 00007f6364832b39 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007f6364a15fac R14: 00007f6364a15fa0 R15: 00007f6364a15fa0
> </TASK>
>
>
> ***
>
> If these findings have caused you to resend the series or submit a
> separate fix, please add the following tag to your commit message:
> Tested-by: syzbot@syzkaller.appspotmail.com
>
> ---
> This report is generated by a bot. It may contain errors.
> syzbot ci engineers can be reached at syzkaller@googlegroups.com.
>
> The email will later be sent to:
> [alice.kernel@fastmail.im alice@isovalent.com andrew@lunn.ch daniel@iogearbox.net davem@davemloft.net dsahern@kernel.org edumazet@google.com fw@strlen.de gal@nvidia.com horms@kernel.org kuba@kernel.org lucien.xin@gmail.com netdev@vger.kernel.org pabeni@redhat.com razor@blackwall.org shuah@kernel.org stfomichev@gmail.com willemdebruijn.kernel@gmail.com]
>
> If the report looks fine to you, reply with:
> #syz upstream
>
> If the report is a false positive, reply with
> #syz invalid
>
> --
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2026-02-27 17:19 [moderation/CI] Re: BIG TCP for UDP tunnels syzbot ci
2026-02-27 18:15 ` Aleksandr Nogikh
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