[v6.6] WARNING in __skb_flow_dissect

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8cee53b8eaeb Linux 6.6.134
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16f260ce580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c5b35c4db8465904
dashboard link: https://syzkaller.appspot.com/bug?extid=0a444a911c34d9b5ca5c
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4c0eb6df7b4a/disk-8cee53b8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/38626ee912e4/vmlinux-8cee53b8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/646a84f3433a/bzImage-8cee53b8.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0a444a...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 14023 at net/core/flow_dissector.c:1107 __skb_flow_dissect+0xbde/0x6d60 net/core/flow_dissector.c:1102
Modules linked in:
CPU: 1 PID: 14023 Comm: syz.3.2334 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:__skb_flow_dissect+0xbde/0x6d60 net/core/flow_dissector.c:1107
Code: db 59 00 00 80 3d 00 aa fd 05 01 0f 85 01 5a 00 00 e8 d6 28 0f f9 e9 17 f9 ff ff e8 cc 28 0f f9 e9 b4 03 00 00 e8 c2 28 0f f9 <0f> 0b e9 00 ff ff ff e8 b6 28 0f f9 c6 05 cb a9 fd 05 01 48 c7 c7
RSP: 0000:ffffc900001ef920 EFLAGS: 00010246
RAX: ffffffff8877f93e RBX: ffff88805448a140 RCX: ffff888024ae1e00
RDX: 0000000000000100 RSI: ffffffff8b1c8e40 RDI: ffffffff8b1c8e00
RBP: ffffc900001eff38 R08: dffffc0000000000 R09: 1ffffffff2238aa0
R10: dffffc0000000000 R11: fffffbfff2238aa1 R12: ffffffff8e8b86b8
R13: ffffffff8877ef59 R14: 0000000000000000 R15: 1ffffffff1d170d8
FS: 00007fac3ae4c6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000093030 CR3: 000000005e69a000 CR4: 00000000003506e0
Call Trace:
<IRQ>
skb_flow_dissect_flow_keys include/linux/skbuff.h:1544 [inline]
___skb_get_hash net/core/flow_dissector.c:1801 [inline]
__skb_get_hash+0xf3/0x2e0 net/core/flow_dissector.c:1866
skb_get_hash include/linux/skbuff.h:1586 [inline]
nft_trace_init+0x1bb/0x410 net/netfilter/nf_tables_trace.c:316
nft_do_chain+0x14fc/0x1600 net/netfilter/nf_tables_core.c:268
nf_route_table_hook6+0x366/0x7b0 net/netfilter/nft_chain_route.c:88
nf_hook_entry_hookfn include/linux/netfilter.h:144 [inline]
nf_hook_slow+0xbd/0x200 net/netfilter/core.c:626
nf_hook include/linux/netfilter.h:259 [inline]
__ip6_local_out+0x784/0x8a0 net/ipv6/output_core.c:143
ip6_local_out+0x2a/0x130 net/ipv6/output_core.c:153
ip6tunnel_xmit include/net/ip6_tunnel.h:161 [inline]
udp_tunnel6_xmit_skb+0x53e/0x970 net/ipv6/ip6_udp_tunnel.c:109
tipc_udp_xmit+0x58d/0xb40 net/tipc/udp_media.c:220
tipc_udp_send_msg+0x27e/0x3e0 net/tipc/udp_media.c:271
tipc_bearer_xmit_skb+0x2ad/0x3f0 net/tipc/bearer.c:575
tipc_disc_timeout+0x596/0x6f0 net/tipc/discover.c:338
call_timer_fn+0x189/0x540 kernel/time/timer.c:1701
expire_timers kernel/time/timer.c:1752 [inline]
__run_timers+0x542/0x800 kernel/time/timer.c:2023
run_timer_softirq+0x67/0xf0 kernel/time/timer.c:2036
handle_softirqs+0x280/0x820 kernel/softirq.c:578
__do_softirq kernel/softirq.c:612 [inline]
invoke_softirq kernel/softirq.c:452 [inline]
__irq_exit_rcu+0xd3/0x190 kernel/softirq.c:661
irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:finish_task_switch+0x26a/0x8f0 kernel/sched/core.c:5255
Code: 0f 84 33 01 00 00 48 85 db 0f 85 52 01 00 00 e9 de 04 00 00 4c 8b 75 d0 4c 89 e7 e8 00 99 32 09 e8 9b 29 30 00 fb 4c 8b 65 c0 <49> 8d bc 24 f8 15 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 28 84 c0
RSP: 0000:ffffc9000d24f298 EFLAGS: 00000282
RAX: a3cc6ffa867e4300 RBX: 0000000000000000 RCX: a3cc6ffa867e4300
RDX: dffffc0000000000 RSI: ffffffff8acac9e0 RDI: ffffffff8b1c8e60
RBP: ffffc9000d24f2f0 R08: ffffffff8e8b14ef R09: 1ffffffff1d1629d
R10: dffffc0000000000 R11: fffffbfff1d1629e R12: ffff888024ae1e00
R13: dffffc0000000000 R14: ffff88802cfc1e00 R15: ffff8880b8f3cac8
context_switch kernel/sched/core.c:5384 [inline]
__schedule+0x155b/0x45a0 kernel/sched/core.c:6700
schedule+0xbd/0x170 kernel/sched/core.c:6774
schedule_timeout+0xc1/0x2d0 kernel/time/timer.c:2144
unix_wait_for_peer+0x1f6/0x2f0 net/unix/af_unix.c:1515
unix_dgram_sendmsg+0xec2/0x16d0 net/unix/af_unix.c:2105
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
____sys_sendmsg+0x5ba/0x960 net/socket.c:2594
___sys_sendmsg+0x2a6/0x360 net/socket.c:2648
__sys_sendmmsg+0x2ca/0x510 net/socket.c:2734
__do_sys_sendmmsg net/socket.c:2763 [inline]
__se_sys_sendmmsg net/socket.c:2760 [inline]
__x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2760
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fac39f9c819
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:00007fac3ae4c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007fac3a215fa0 RCX: 00007fac39f9c819
RDX: 0000000000000318 RSI: 00002000000bd000 RDI: 0000000000000004
RBP: 00007fac3a032c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fac3a216038 R14: 00007fac3a215fa0 R15: 00007fffa2cc5ea8
</TASK>
----------------
Code disassembly (best guess):
0: 0f 84 33 01 00 00 je 0x139
6: 48 85 db test %rbx,%rbx
9: 0f 85 52 01 00 00 jne 0x161
f: e9 de 04 00 00 jmp 0x4f2
14: 4c 8b 75 d0 mov -0x30(%rbp),%r14
18: 4c 89 e7 mov %r12,%rdi
1b: e8 00 99 32 09 call 0x9329920
20: e8 9b 29 30 00 call 0x3029c0
25: fb sti
26: 4c 8b 65 c0 mov -0x40(%rbp),%r12
* 2a: 49 8d bc 24 f8 15 00 lea 0x15f8(%r12),%rdi <-- trapping instruction
31: 00
32: 48 89 f8 mov %rdi,%rax
35: 48 c1 e8 03 shr $0x3,%rax
39: 42 0f b6 04 28 movzbl (%rax,%r13,1),%eax
3e: 84 c0 test %al,%al


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