[syzbot] [net?] WARNING in u32_change (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a95f71ad3e2e Merge tag 'for-linus' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15c27c02580000
kernel config: https://syzkaller.appspot.com/x/.config?x=65722f41f7edc17e
dashboard link: https://syzkaller.appspot.com/bug?extid=d5ace703ed883df56e42
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12b189e6580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=134c0006580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-a95f71ad.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cef9447ff4b5/vmlinux-a95f71ad.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a1176fe9ea48/bzImage-a95f71ad.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d5ace7...@syzkaller.appspotmail.com

netlink: 44 bytes leftover after parsing attributes in process `syz.0.17'.
------------[ cut here ]------------
memcpy: detected field-spanning write (size 32) of single field "&new->sel" at net/sched/cls_u32.c:855 (size 16)
WARNING: net/sched/cls_u32.c:855 at u32_init_knode net/sched/cls_u32.c:855 [inline], CPU#0: syz.0.17/5487
WARNING: net/sched/cls_u32.c:855 at u32_change+0x1da0/0x2720 net/sched/cls_u32.c:921, CPU#0: syz.0.17/5487
Modules linked in:
CPU: 0 UID: 0 PID: 5487 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:u32_init_knode net/sched/cls_u32.c:855 [inline]
RIP: 0010:u32_change+0x1daf/0x2720 net/sched/cls_u32.c:921
Code: 3d 4c eb 42 06 01 75 33 e8 0e 0e 0d f8 eb 50 e8 07 0e 0d f8 48 8d 3d 00 1f 68 06 b9 10 00 00 00 4c 89 f6 48 c7 c2 00 64 e1 8c <67> 48 0f b9 3a e9 af ee ff ff e8 e2 0d 0d f8 eb 24 e8 db 0d 0d f8
RSP: 0018:ffffc90004976fc0 EFLAGS: 00010293
RAX: ffffffff89b88e29 RBX: ffff888038a7c800 RCX: 0000000000000010
RDX: ffffffff8ce16400 RSI: 0000000000000020 RDI: ffffffff9020ad30
RBP: ffffc90004977178 R08: 0000000000000dc0 R09: 00000000ffffffff
R10: dffffc0000000000 R11: fffffbfff20232f7 R12: ffff888033a63ce8
R13: 0000000000000001 R14: 0000000000000020 R15: 0000000000000001
FS: 00005555621f5500(0000) GS:ffff88808ca5b000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe0048eff8 CR3: 000000005563f000 CR4: 0000000000352ef0
Call Trace:
<TASK>
tc_new_tfilter+0xe1c/0x1630 net/sched/cls_api.c:2423
rtnetlink_rcv_msg+0x7d5/0xbe0 net/core/rtnetlink.c:6958
netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550
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_sendmmsg+0x27c/0x4e0 net/socket.c:2735
__do_sys_sendmmsg net/socket.c:2762 [inline]
__se_sys_sendmmsg net/socket.c:2759 [inline]
__x64_sys_sendmmsg+0xa0/0xc0 net/socket.c:2759
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: 0033:0x7f78ead9c629
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:00007fff46c64d98 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f78eb015fa0 RCX: 00007f78ead9c629
RDX: 04000000000001f2 RSI: 0000200000000000 RDI: 0000000000000004
RBP: 00007f78eae32b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f78eb015fac R14: 00007f78eb015fa0 R15: 00007f78eb015fa0
</TASK>
----------------
Code disassembly (best guess):
0: 3d 4c eb 42 06 cmp $0x642eb4c,%eax
5: 01 75 33 add %esi,0x33(%rbp)
8: e8 0e 0e 0d f8 call 0xf80d0e1b
d: eb 50 jmp 0x5f
f: e8 07 0e 0d f8 call 0xf80d0e1b
14: 48 8d 3d 00 1f 68 06 lea 0x6681f00(%rip),%rdi # 0x6681f1b
1b: b9 10 00 00 00 mov $0x10,%ecx
20: 4c 89 f6 mov %r14,%rsi
23: 48 c7 c2 00 64 e1 8c mov $0xffffffff8ce16400,%rdx
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: e9 af ee ff ff jmp 0xffffeee3
34: e8 e2 0d 0d f8 call 0xf80d0e1b
39: eb 24 jmp 0x5f
3b: e8 db 0d 0d f8 call 0xf80d0e1b


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