From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f200.google.com (mail-oi1-f200.google.com [209.85.167.200]) (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 64A023AE6F6 for ; Sat, 28 Feb 2026 22:12:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.200 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772316755; cv=none; b=uPuYUnamf7uSeFFtOumQVKZEkQnHNk6e97kR5gGLgkKxGoNR7hSPvomLoL19Yg75rnipFhEbfX9Q0FE66pmvGuvkeRJQlasXngkczkE675vx09+pZdeTzGJmMstcQF2tA/j+n/+UBIrn+1Z2NlipShHagCQNDsfS4bA3ZRFe1HY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772316755; c=relaxed/simple; bh=KHeLoS7BWEI46FzR9qGtupaLwwefG46tni6wMTwbQ/s=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To:Cc: Content-Type; b=kKzK10EALxFNpBI+1VUA3FaJeeVBuxrCnJ+umh7XY00pGAoHwzRL4Phw7AkvO5/U8pMX1VmXz1mvWw8PL3Mw1/W/50h0MuBR5YVXWKuqFNdly9bf1JWGuYPQOuwvG5d3nuiD0TpC3bz3YS8yOY37hlSXTjkpUjuXLg/tUIULB/s= 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=209.85.167.200 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-f200.google.com with SMTP id 5614622812f47-464a2e39173so37393974b6e.1 for ; Sat, 28 Feb 2026 14:12:34 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1772316753; x=1772921553; h=cc:to:from:subject:message-id:in-reply-to:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=g4lrXEHcsBV4g6kjs5fV0GLXi7ODwUGzXXo88xd8ebI=; b=cBjXbAkh6rxkyijl3IaeOSJWHx4ADKC6LdhG4BTFhRClkYzPFLvDc8ZMJdXWDYiiny c9Ll93CLH6Y7vJa+or1eoLzCW7ObEdT+USwL4frBu8w9yZ4vQt4q+vcnL6TTtSp/kCkd J/8nQw6eo6dQaKe235G3inWE/L+jhl+aiMFYtgJL2Oe6IUYaHqwkEjYp1kuXDlc7rrkl BHrjx5APjrSD9lzSyyQp5lAfouUZ0NStzXJIaO7XvoEPIQvsm5XQ7ClCJCGRx0V/kk4O /CecHi9u0ycoZOXkkUdhVZQuss6mVkLObCQDA/+sUKZPrhzZHHTvWxorSIqCd+k2XNFv 4lyQ== X-Forwarded-Encrypted: i=1; AJvYcCUbA0Q5HiwpTlBwQ+YCY6U6lmLzxwr/VdwJSvgfmfnt94dLL2jXfhFv8kOGBpC5knctYsMnU9w=@vger.kernel.org X-Gm-Message-State: AOJu0YwMkeLmyA/bQmxkyBPq9HHLfhe4ebI3rlDm3FN+p4DpD9kvITlK FskoO3OVqKTB4Qkp1hhm2hcfx9ksDpRxxjSbVVBxac4l9yU1j3kb2FsH8GNP9xzse6MOTtMpRZD cgfJrz6itt/TtkUs03cTLjo18cWHPQBNSw9PnWroLm6koTdqWlsiLJrSZe2M= Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:808:b0:662:fe9f:2259 with SMTP id 006d021491bc7-679faf2678bmr4493097eaf.50.1772316753493; Sat, 28 Feb 2026 14:12:33 -0800 (PST) Date: Sat, 28 Feb 2026 14:12:33 -0800 In-Reply-To: <20260227220740.11928-1-mail@david-bauer.net> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69a36851.050a0220.3a55be.0047.GAE@google.com> Subject: [syzbot ci] Re: l2tp: account for IP version in SKB headroom From: syzbot ci 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 Cc: syzbot@lists.linux.dev, syzkaller-bugs@googlegroups.com 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.