syzbot


WARNING in __skb_vlan_pop

Status: closed as invalid on 2026/01/07 12:42
Subsystems: bridge
[Documentation on labels]
First crash: 90d, last: 90d

Sample crash report:
------------[ cut here ]------------
__skb_vlan_pop got skb with skb->data not at mac header (offset 14)
WARNING: CPU: 0 PID: 26126 at net/core/skbuff.c:6310 __skb_vlan_pop+0x703/0x890 net/core/skbuff.c:6310
Modules linked in:
CPU: 0 UID: 0 PID: 26126 Comm: syz.1.2777 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:__skb_vlan_pop+0x703/0x890 net/core/skbuff.c:6310
Code: 31 ff 89 de e8 8e c2 8f f8 84 db 75 21 e8 a5 c7 8f f8 c6 05 f4 4f 3d 07 01 90 48 c7 c7 e0 88 be 8c 44 89 ee e8 3e f7 4d f8 90 <0f> 0b 90 90 c7 44 24 08 ea ff ff ff e9 ce fd ff ff 4c 89 ff e8 d4
RSP: 0018:ffffc9000471f1d0 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff817b3ee8
RDX: ffff88802c4ba480 RSI: ffffffff817b3ef5 RDI: 0000000000000001
RBP: ffffc9000471f238 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff88803d5a63c2
R13: 000000000000000e R14: ffff88801302f398 R15: ffff88801302f37a
FS:  00007fef275b56c0(0000) GS:ffff8880d6a08000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fef275b4f98 CR3: 00000000479f6000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 skb_vlan_pop+0x174/0x280 net/core/skbuff.c:6359
 br_handle_egress_vlan_tunnel+0x147/0x990 net/bridge/br_vlan_tunnel.c:202
 br_handle_vlan+0x478/0x550 net/bridge/br_vlan.c:527
 __br_forward+0x95/0x5b0 net/bridge/br_forward.c:87
 br_flood+0x4c4/0x650 net/bridge/br_forward.c:252
 br_dev_xmit+0x14d1/0x1880 net/bridge/br_device.c:112
 __netdev_start_xmit include/linux/netdevice.h:5248 [inline]
 netdev_start_xmit include/linux/netdevice.h:5257 [inline]
 xmit_one net/core/dev.c:3845 [inline]
 dev_hard_start_xmit+0x97/0x740 net/core/dev.c:3861
 __dev_queue_xmit+0xa46/0x4490 net/core/dev.c:4763
 dev_queue_xmit include/linux/netdevice.h:3365 [inline]
 packet_xmit+0x23e/0x360 net/packet/af_packet.c:275
 packet_snd net/packet/af_packet.c:3076 [inline]
 packet_sendmsg+0x2756/0x5850 net/packet/af_packet.c:3108
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xa98/0xc70 net/socket.c:2630
 ___sys_sendmsg+0x134/0x1d0 net/socket.c:2684
 __sys_sendmsg+0x16d/0x220 net/socket.c:2716
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fef2678f6c9
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:00007fef275b5038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fef269e6090 RCX: 00007fef2678f6c9
RDX: 0000000000000000 RSI: 00002000000001c0 RDI: 0000000000000005
RBP: 00007fef26811f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fef269e6128 R14: 00007fef269e6090 R15: 00007ffd30d28698
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/03 20:36 upstream 6146a0f1dfae e6c64ba8 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in __skb_vlan_pop
* Struck through repros no longer work on HEAD.