From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f197.google.com (mail-oi1-f197.google.com [209.85.167.197]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B6C3B317153 for ; Sat, 28 Feb 2026 21:57:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.197 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772315855; cv=none; b=rx8/33sLlL3atcrlBFVoGbBQZdN7G89rfmjbcN+HWFWlJ8nEdFpLtpwu3V5cOL/Ih4OKvDiYfKY2/wqyCT/ScwdVIQXW0yyR0n8DaHWwOSMN8xn9Y7Up0eOIqFP+G0RnRwzoRWWtq6EHlSV4oz7xv2YY59SPg+HEOezUG3bltj4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772315855; c=relaxed/simple; bh=FIRn1+8ax2Lv3XtBmcOtQu1gkUwhsZDiRONIGBIrxuM=; h=MIME-Version:Date:Message-ID:Subject:From:To:Cc:Content-Type; b=VxH83AJ2fVJsT3huKTA6Y8qAEu5kvo4aQMK+Z9F/kgRKecmSn5/k0lcSIykHc0QvqxfTyeVi+tnFlBf74plKEugmIF/q29vWvaBd12O3inI+6RajgatZWoawh4nIln1gsAmVfq/FUuq1Vknq9WyapRp/+/IsNGSe5RZA9tgQD3s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.167.197 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oi1-f197.google.com with SMTP id 5614622812f47-463a075e177so18223156b6e.2 for ; Sat, 28 Feb 2026 13:57:33 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1772315852; x=1772920652; h=cc:to:from:subject:message-id:date:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=EaVdJqqyJBfDjiHxrQjMx7hvTBX3XPQ0F0eTxjZm8TQ=; b=ZutXltlzwMK+uOQOPHpMi5Mpb8FtEfEWzhRC7QL7ruYzPjipNZINtBNcF1P5PckJc8 MalDl/zMh7jOrMBlXzrLd+ISTIBOcrXowkIUNXaBRZ5cakRzJIghkc+gOyemdnBWdqD1 qRd/bfnKE2ZyIITr0+WXTL4iued0rJYr/Gq7r06mbXMx0REv1NL7ZOG7Kv+YaPQ9KSpI NIslpipIoWuoR7HTYg9n8Gy0EY6hsUugQMGX6ZgQF0zk6qDjurvHyQLffBT3C/XBOfTG IxocxhFYXO+9W5j0k+sQzrLnRbDv4DIgbaqhsAo0wEZx91xC4W9h/LvKKODHXTfidAJ0 GPxA== X-Gm-Message-State: AOJu0Ywj5bjgX0fvEgoxNAwZaLUTMShQUMuHaMrqxL4P4KjuKch2yPqU ddtG7aadT1uCcnPsPfX4LfgMovlSRRaQeD4sAnicde0C4n5dpn5Rml7YZsJxFR0jNjuS1fHJHAl JF5GzvpQjQE80ECxbWn8STCM9b8cReoXfsma4L9hc9JFHLUGzrpU8r+Ttn3Y= Precedence: bulk X-Mailing-List: syzbot@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:1c9a:b0:65f:5b63:2bd with SMTP id 006d021491bc7-679fadd7e6fmr3858636eaf.16.1772315852595; Sat, 28 Feb 2026 13:57:32 -0800 (PST) Date: Sat, 28 Feb 2026 13:57:32 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69a364cc.050a0220.16a3f7.0001.GAE@google.com> Subject: [moderation/CI] Re: l2tp: account for IP version in SKB headroom From: syzbot ci To: syzkaller-upstream-moderation@googlegroups.com Cc: syzbot@lists.linux.dev Content-Type: text/plain; charset="UTF-8" syzbot ci has tested the following series [v1] l2tp: account for IP version in SKB headroom https://lore.kernel.org/all/20260227220740.11928-1-mail@david-bauer.net * [PATCH net-next 1/2] l2tp: account for IP version in SKB headroom * [PATCH net-next 2/2] l2tp: unify headroom calculation and found the following issue: general protection fault in l2tp_eth_create Full report is available here: https://ci.syzbot.org/series/10f6234e-88a0-41c8-b9d2-a3e54f289fbd *** general protection fault in l2tp_eth_create tree: net-next URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net-next.git base: 58e443b773ef054ae069cf777ba19adb99d73829 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/66fb3a44-8edb-4c92-9149-328653e46ccd/config C repro: https://ci.syzbot.org/findings/9b3d30fe-b87f-4b00-99a6-464f0a271312/c_repro syz repro: https://ci.syzbot.org/findings/9b3d30fe-b87f-4b00-99a6-464f0a271312/syz_repro netlink: 8 bytes leftover after parsing attributes in process `syz.0.17'. Oops: general protection fault, probably for non-canonical address 0xdffffc0000000012: 0000 [#1] SMP KASAN PTI KASAN: null-ptr-deref in range [0x0000000000000090-0x0000000000000097] CPU: 1 UID: 0 PID: 5971 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:l2tp_session_udp_hdrlen net/l2tp/l2tp_core.h:340 [inline] RIP: 0010:l2tp_session_overhead net/l2tp/l2tp_core.h:346 [inline] RIP: 0010:l2tp_eth_adjust_mtu net/l2tp/l2tp_eth.c:202 [inline] RIP: 0010:l2tp_eth_create+0x2cd/0xca0 net/l2tp/l2tp_eth.c:250 Code: 48 89 44 24 58 42 80 3c 28 00 74 08 48 89 df e8 b9 68 54 f7 48 89 5c 24 60 4c 8b 33 4d 8d a6 94 00 00 00 4c 89 e0 48 c1 e8 03 <42> 0f b6 04 28 84 c0 0f 85 35 08 00 00 45 8b 24 24 31 ff 44 89 e6 RSP: 0018:ffffc900040c7160 EFLAGS: 00010207 RAX: 0000000000000012 RBX: ffff888114d00020 RCX: 0000000000000000 RDX: ffff888104f90000 RSI: 0000000000000028 RDI: 0000000000000000 RBP: ffffc900040c7270 R08: 0000000000400dc0 R09: 00000000ffffffff R10: dffffc0000000000 R11: fffffbfff2022f77 R12: 0000000000000094 R13: dffffc0000000000 R14: 0000000000000000 R15: ffff888114d00000 FS: 0000555574b08500(0000) GS:ffff8882a9467000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055a269259270 CR3: 0000000105770000 CR4: 00000000000006f0 Call Trace: l2tp_nl_cmd_session_create+0x766/0xc60 net/l2tp/l2tp_netlink.c:639 genl_family_rcv_msg_doit+0x22a/0x330 net/netlink/genetlink.c:1114 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] genl_rcv_msg+0x61c/0x7a0 net/netlink/genetlink.c:1209 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg net/socket.c:742 [inline] ____sys_sendmsg+0xa68/0xad0 net/socket.c:2592 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2646 __sys_sendmsg net/socket.c:2678 [inline] __do_sys_sendmsg net/socket.c:2683 [inline] __se_sys_sendmsg net/socket.c:2681 [inline] __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681 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: 0033:0x7f371079c799 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:00007fff7e0100f8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f3710a15fa0 RCX: 00007f371079c799 RDX: 0000000020000034 RSI: 0000200000000140 RDI: 0000000000000005 RBP: 00007f3710832bd9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f3710a15fac R14: 00007f3710a15fa0 R15: 00007f3710a15fa0 Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:l2tp_session_udp_hdrlen net/l2tp/l2tp_core.h:340 [inline] RIP: 0010:l2tp_session_overhead net/l2tp/l2tp_core.h:346 [inline] RIP: 0010:l2tp_eth_adjust_mtu net/l2tp/l2tp_eth.c:202 [inline] RIP: 0010:l2tp_eth_create+0x2cd/0xca0 net/l2tp/l2tp_eth.c:250 Code: 48 89 44 24 58 42 80 3c 28 00 74 08 48 89 df e8 b9 68 54 f7 48 89 5c 24 60 4c 8b 33 4d 8d a6 94 00 00 00 4c 89 e0 48 c1 e8 03 <42> 0f b6 04 28 84 c0 0f 85 35 08 00 00 45 8b 24 24 31 ff 44 89 e6 RSP: 0018:ffffc900040c7160 EFLAGS: 00010207 RAX: 0000000000000012 RBX: ffff888114d00020 RCX: 0000000000000000 RDX: ffff888104f90000 RSI: 0000000000000028 RDI: 0000000000000000 RBP: ffffc900040c7270 R08: 0000000000400dc0 R09: 00000000ffffffff R10: dffffc0000000000 R11: fffffbfff2022f77 R12: 0000000000000094 R13: dffffc0000000000 R14: 0000000000000000 R15: ffff888114d00000 FS: 0000555574b08500(0000) GS:ffff8882a9467000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055a269259270 CR3: 0000000105770000 CR4: 00000000000006f0 ---------------- Code disassembly (best guess): 0: 48 89 44 24 58 mov %rax,0x58(%rsp) 5: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) a: 74 08 je 0x14 c: 48 89 df mov %rbx,%rdi f: e8 b9 68 54 f7 call 0xf75468cd 14: 48 89 5c 24 60 mov %rbx,0x60(%rsp) 19: 4c 8b 33 mov (%rbx),%r14 1c: 4d 8d a6 94 00 00 00 lea 0x94(%r14),%r12 23: 4c 89 e0 mov %r12,%rax 26: 48 c1 e8 03 shr $0x3,%rax * 2a: 42 0f b6 04 28 movzbl (%rax,%r13,1),%eax <-- trapping instruction 2f: 84 c0 test %al,%al 31: 0f 85 35 08 00 00 jne 0x86c 37: 45 8b 24 24 mov (%r12),%r12d 3b: 31 ff xor %edi,%edi 3d: 44 89 e6 mov %r12d,%esi *** 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: [davem@davemloft.net edumazet@google.com horms@kernel.org kuba@kernel.org linux-kernel@vger.kernel.org mail@david-bauer.net netdev@vger.kernel.org pabeni@redhat.com] If the report looks fine to you, reply with: #syz upstream If the report is a false positive, reply with #syz invalid