[v6.1] WARNING in u32_change

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 779f9571ac3e Linux 6.1.164
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16f03722580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b1adc0bfde2d8a4a
dashboard link: https://syzkaller.appspot.com/bug?extid=512f29e28a6f2f187bd0
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/85e761437fc4/disk-779f9571.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0f3aa7ae77ae/vmlinux-779f9571.xz
kernel image: https://storage.googleapis.com/syzbot-assets/baba59a67bd9/Image-779f9571.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+512f29...@syzkaller.appspotmail.com

------------[ cut here ]------------
memcpy: detected field-spanning write (size 32) of single field "&new->sel" at net/sched/cls_u32.c:854 (size 16)
WARNING: CPU: 1 PID: 4574 at net/sched/cls_u32.c:854 u32_init_knode net/sched/cls_u32.c:854 [inline]
WARNING: CPU: 1 PID: 4574 at net/sched/cls_u32.c:854 u32_change+0x1698/0x1f18 net/sched/cls_u32.c:920
Modules linked in:
CPU: 1 PID: 4574 Comm: syz.4.77 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/03/2025
pstate: 62400005 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : u32_init_knode net/sched/cls_u32.c:854 [inline]
pc : u32_change+0x1698/0x1f18 net/sched/cls_u32.c:920
lr : u32_init_knode net/sched/cls_u32.c:854 [inline]
lr : u32_change+0x1698/0x1f18 net/sched/cls_u32.c:920
sp : ffff800020d26be0
x29: ffff800020d26d40 x28: ffff0000d2411e00 x27: 0000000000000000
x26: 1fffe0001a4823cd x25: ffff0000d2410a00 x24: ffff0000d2411a00
x23: 0000000000000010 x22: ffff7000041a4d8c x21: dfff800000000000
x20: ffff800020d27400 x19: ffff800017bd9000 x18: ffff800011b8bf60
x17: 1fffe00033eac97e x16: ffff8000082d9364 x15: 0000000040000000
x14: 0000000000000001 x13: 1fffe00033eaf030 x12: 0000000000ff0100
x11: ff0080000a8da424 x10: 0000000000000003 x9 : 69a76cf98f06be00
x8 : 69a76cf98f06be00 x7 : ffff80000825796c x6 : 0000000000000000
x5 : 0000000000000080 x4 : 0000000000000001 x3 : 0000000000000000
x2 : 0000000000000006 x1 : ffff800011b8da80 x0 : ffff80018a3ff000
Call trace:
u32_init_knode net/sched/cls_u32.c:854 [inline]
u32_change+0x1698/0x1f18 net/sched/cls_u32.c:920
tc_new_tfilter+0xc28/0x1370 net/sched/cls_api.c:2187
rtnetlink_rcv_msg+0x6d8/0xcdc net/core/rtnetlink.c:6141
netlink_rcv_skb+0x218/0x3e8 net/netlink/af_netlink.c:2511
rtnetlink_rcv+0x28/0x38 net/core/rtnetlink.c:6168
netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
netlink_unicast+0x60c/0x814 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x6f4/0x9c0 net/netlink/af_netlink.c:1872
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg net/socket.c:730 [inline]
____sys_sendmsg+0x5c8/0x938 net/socket.c:2518
___sys_sendmsg net/socket.c:2572 [inline]
__sys_sendmmsg+0x344/0x834 net/socket.c:2658
__do_sys_sendmmsg net/socket.c:2687 [inline]
__se_sys_sendmmsg net/socket.c:2684 [inline]
__arm64_sys_sendmmsg+0xa0/0xbc net/socket.c:2684
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b4 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
irq event stamp: 1252
hardirqs last enabled at (1251): [<ffff800008257a00>] raw_spin_rq_unlock_irq kernel/sched/sched.h:1374 [inline]
hardirqs last enabled at (1251): [<ffff800008257a00>] finish_lock_switch+0xb0/0x1c4 kernel/sched/core.c:5004
hardirqs last disabled at (1252): [<ffff800011a22ed4>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:405
softirqs last enabled at (1244): [<ffff8000081ac37c>] softirq_handle_end kernel/softirq.c:439 [inline]
softirqs last enabled at (1244): [<ffff8000081ac37c>] handle_softirqs+0xaec/0xc60 kernel/softirq.c:624
softirqs last disabled at (1107): [<ffff800008020164>] __do_softirq+0x14/0x20 kernel/softirq.c:630
---[ end trace 0000000000000000 ]---


---
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[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7a137e9bfa0e Linux 6.6.127
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=105da55a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2a950bf7c0bff9f9
dashboard link: https://syzkaller.appspot.com/bug?extid=b98f25656b791725fc13

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/04a02efb4a79/disk-7a137e9b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f7b848f192f0/vmlinux-7a137e9b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/77a981f90b3d/bzImage-7a137e9b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by: syzbot+b98f25...@syzkaller.appspotmail.com

netlink: 44 bytes leftover after parsing attributes in process `syz.3.2719'.
------------[ cut here ]------------
memcpy: detected field-spanning write (size 32) of single field "&new->sel" at net/sched/cls_u32.c:855 (size 16)
WARNING: CPU: 0 PID: 13175 at net/sched/cls_u32.c:855 u32_init_knode net/sched/cls_u32.c:855 [inline]
WARNING: CPU: 0 PID: 13175 at net/sched/cls_u32.c:855 u32_change+0x1c5a/0x24f0 net/sched/cls_u32.c:921
Modules linked in:
CPU: 0 PID: 13175 Comm: syz.3.2719 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:u32_init_knode net/sched/cls_u32.c:855 [inline]
RIP: 0010:u32_change+0x1c5a/0x24f0 net/sched/cls_u32.c:921
Code: f8 eb 59 e8 a8 a0 d9 f8 c6 05 51 12 c8 05 01 b9 10 00 00 00 48 c7 c7 e0 40 c7 8b 4c 89 f6 48 c7 c2 60 41 c7 8b e8 16 62 a3 f8 <0f> 0b e9 86 f0 ff ff e8 7a a0 d9 f8 eb 24 e8 73 a0 d9 f8 c6 05 f3
RSP: 0018:ffffc9000bb9ed40 EFLAGS: 00010246
RAX: 5d780ffa87e23600 RBX: ffff88802f317000 RCX: 0000000000080000
RDX: ffffc900123c8000 RSI: 0000000000005db6 RDI: 0000000000005db7
RBP: ffffc9000bb9eef8 R08: ffffc9000bb9e947 R09: 1ffff92001773d28
R10: dffffc0000000000 R11: fffff52001773d29 R12: ffff88802f314400
R13: ffff88802f3144e8 R14: 0000000000000020 R15: ffff88807ea4d7c0
FS: 00007fa5366c06c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3e59be9d40 CR3: 000000006bb6e000 CR4: 00000000003526f0
Call Trace:
<TASK>
tc_new_tfilter+0xe4f/0x1640 net/sched/cls_api.c:2347
rtnetlink_rcv_msg+0x8b8/0xfa0 net/core/rtnetlink.c:6463
netlink_rcv_skb+0x241/0x4d0 net/netlink/af_netlink.c:2545
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x751/0x8d0 net/netlink/af_netlink.c:1346
netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1894
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: 0033:0x7fa53579c629
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:00007fa5366c0028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007fa535a15fa0 RCX: 00007fa53579c629
RDX: 04000000000001f2 RSI: 0000200000000000 RDI: 0000000000000006
RBP: 00007fa535832b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa535a16038 R14: 00007fa535a15fa0 R15: 00007fffac1971a8
</TASK>

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 779f9571ac3e Linux 6.1.164
git tree: linux-6.1.y

console output: https://syzkaller.appspot.com/x/log.txt?x=1643a55a580000

kernel config: https://syzkaller.appspot.com/x/.config?x=b1adc0bfde2d8a4a
dashboard link: https://syzkaller.appspot.com/bug?extid=512f29e28a6f2f187bd0
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17f34152580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17fd055a580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/85e761437fc4/disk-779f9571.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0f3aa7ae77ae/vmlinux-779f9571.xz
kernel image: https://storage.googleapis.com/syzbot-assets/baba59a67bd9/Image-779f9571.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+512f29...@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:854 (size 16)

WARNING: CPU: 1 PID: 4453 at net/sched/cls_u32.c:854 u32_init_knode net/sched/cls_u32.c:854 [inline]
WARNING: CPU: 1 PID: 4453 at net/sched/cls_u32.c:854 u32_change+0x1698/0x1f18 net/sched/cls_u32.c:920
Modules linked in:
CPU: 1 PID: 4453 Comm: syz.0.17 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/03/2025
pstate: 62400005 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : u32_init_knode net/sched/cls_u32.c:854 [inline]
pc : u32_change+0x1698/0x1f18 net/sched/cls_u32.c:920
lr : u32_init_knode net/sched/cls_u32.c:854 [inline]
lr : u32_change+0x1698/0x1f18 net/sched/cls_u32.c:920

sp : ffff800021436be0
x29: ffff800021436d40 x28: ffff0000c2eff600 x27: 0000000000000000
x26: 1fffe000185dfecd x25: ffff0000cb6dc800 x24: ffff0000cb6a6000
x23: 0000000000000010 x22: ffff700004286d8c x21: dfff800000000000
x20: ffff800021437400 x19: ffff800017bd9000 x18: 0000000000000000
x17: 20646c6569662065 x16: ffff8000082d9364 x15: 0000000000000000
x14: 0000000000000001 x13: 1fffe00033eac9a3 x12: 0000000000ff0100
x11: ff00800008194238 x10: 0000000000000000 x9 : c3210f00bd4d3500
x8 : c3210f00bd4d3500 x7 : 0000000000000001 x6 : 0000000000000001
x5 : ffff800021436678 x4 : ffff8000152f4cc0 x3 : ffff800008538704
x2 : 0000000000000001 x1 : 0000000100000000 x0 : 0000000000000000

irq event stamp: 2046
hardirqs last enabled at (2045): [<ffff80000830fb6c>] __up_console_sem+0xb4/0xfc kernel/printk/printk.c:261
hardirqs last disabled at (2046): [<ffff800011a22ed4>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:405
softirqs last enabled at (2010): [<ffff80000fdc857c>] local_bh_enable+0x10/0x34 include/linux/bottom_half.h:32
softirqs last disabled at (2002): [<ffff80000fdc8548>] local_bh_disable+0x10/0x34 include/linux/bottom_half.h:19

---[ end trace 0000000000000000 ]---

Zero length message leads to an empty skb


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 7a137e9bfa0e Linux 6.6.127
git tree: linux-6.6.y

console output: https://syzkaller.appspot.com/x/log.txt?x=154b055a580000

kernel config: https://syzkaller.appspot.com/x/.config?x=2a950bf7c0bff9f9
dashboard link: https://syzkaller.appspot.com/bug?extid=b98f25656b791725fc13
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=13dffc02580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14ac3722580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/04a02efb4a79/disk-7a137e9b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f7b848f192f0/vmlinux-7a137e9b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/77a981f90b3d/bzImage-7a137e9b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b98f25...@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: CPU: 0 PID: 5916 at net/sched/cls_u32.c:855 u32_init_knode net/sched/cls_u32.c:855 [inline]
WARNING: CPU: 0 PID: 5916 at net/sched/cls_u32.c:855 u32_change+0x1c5a/0x24f0 net/sched/cls_u32.c:921
Modules linked in:
CPU: 0 PID: 5916 Comm: syz.0.17 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:u32_init_knode net/sched/cls_u32.c:855 [inline]
RIP: 0010:u32_change+0x1c5a/0x24f0 net/sched/cls_u32.c:921
Code: f8 eb 59 e8 a8 a0 d9 f8 c6 05 51 12 c8 05 01 b9 10 00 00 00 48 c7 c7 e0 40 c7 8b 4c 89 f6 48 c7 c2 60 41 c7 8b e8 16 62 a3 f8 <0f> 0b e9 86 f0 ff ff e8 7a a0 d9 f8 eb 24 e8 73 a0 d9 f8 c6 05 f3

RSP: 0018:ffffc900045ded40 EFLAGS: 00010246
RAX: 7639567725e9cd00 RBX: ffff888021abd000 RCX: ffff8880248bda00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: ffffc900045deef8 R08: ffffc900045de947 R09: 1ffff920008bbd28
R10: dffffc0000000000 R11: fffff520008bbd29 R12: ffff88806c6d2800
R13: ffff88806c6d28e8 R14: 0000000000000020 R15: ffff88801f740000
FS: 00005555672a7500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007ffcffdb4c04 CR3: 0000000022276000 CR4: 00000000003506f0

Call Trace:
<TASK>
tc_new_tfilter+0xe4f/0x1640 net/sched/cls_api.c:2347
rtnetlink_rcv_msg+0x8b8/0xfa0 net/core/rtnetlink.c:6463
netlink_rcv_skb+0x241/0x4d0 net/netlink/af_netlink.c:2545
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x751/0x8d0 net/netlink/af_netlink.c:1346
netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1894
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: 0033:0x7f9171d9c629

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:00007fff18912678 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f9172015fa0 RCX: 00007f9171d9c629
RDX: 04000000000001f2 RSI: 0000200000000000 RDI: 0000000000000004
RBP: 00007f9171e32b39 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007f9172015fac R14: 00007f9172015fa0 R15: 00007f9172015fa0
</TASK>