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AJvYcCWxrANX8o5FhQSPk74USaUeZ/Wo4RhrJdXXmIBIxACIljnEHeTvLWECx8MVe8PMWslcgex2cmY=@vger.kernel.org X-Gm-Message-State: AOJu0YwvtFWnmFACVdP45HkKCEGaasrUUo7QzgEp7brJD61TRhkSLznt UWPLtAC/9wYxpnuiI8yGw9YQp7LHIzkK3RNq3nHoqz0VCA/Bs22hHj4+X1Gx+NYLYcantOjyqQc 9PmGNEuVctyl9BavisVO/0QLWm4DXJhf54Qa2VdhpYHkdQ7V1Bf8lk1cbld8= Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:8189:b0:675:2e2e:569c with SMTP id 006d021491bc7-679fae11f43mr2370432eaf.25.1772216250636; Fri, 27 Feb 2026 10:17:30 -0800 (PST) Date: Fri, 27 Feb 2026 10:17:30 -0800 In-Reply-To: <20260226201600.222044-1-alice.kernel@fastmail.im> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69a1dfba.050a0220.3a55be.0026.GAE@google.com> Subject: [syzbot ci] Re: BIG TCP for UDP tunnels From: syzbot ci 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 Cc: syzbot@lists.linux.dev, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" 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: 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 *** 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.