syzbot

netlink: 44 bytes leftover after parsing attributes in process `syz.0.17'.
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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: 4508 at net/sched/cls_u32.c:854 u32_init_knode net/sched/cls_u32.c:854 [inline]
WARNING: CPU: 1 PID: 4508 at net/sched/cls_u32.c:854 u32_change+0x1698/0x1f18 net/sched/cls_u32.c:920
Modules linked in:
CPU: 1 PID: 4508 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 : ffff800020de6be0
x29: ffff800020de6d40 x28: ffff0000ca0b5600 x27: 0000000000000000
x26: 1fffe00019416acd x25: ffff0000cbef6400 x24: ffff0000ca0b4600
x23: 0000000000000010 x22: ffff7000041bcd8c x21: dfff800000000000
x20: ffff800020de7400 x19: ffff800017bd9000 x18: 0000000000000000
x17: 20646c6569662065 x16: ffff8000082d9364 x15: 0000000000000000
x14: 0000000000000001 x13: 1fffe00033eac9a3 x12: 0000000000ff0100
x11: ff00800008194238 x10: 0000000000000000 x9 : 0e7593d2c2233400
x8 : 0e7593d2c2233400 x7 : 0000000000000001 x6 : 0000000000000001
x5 : ffff800020de6678 x4 : ffff8000152f4cc0 x3 : ffff800008538704
x2 : 0000000000000001 x1 : 0000000100000000 x0 : 0000000000000000
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: 3208
hardirqs last  enabled at (3207): [<ffff80000830fb6c>] __up_console_sem+0xb4/0xfc kernel/printk/printk.c:261
hardirqs last disabled at (3208): [<ffff800011a22ed4>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:405
softirqs last  enabled at (3166): [<ffff80000fdc857c>] local_bh_enable+0x10/0x34 include/linux/bottom_half.h:32
softirqs last disabled at (3158): [<ffff80000fdc8548>] local_bh_disable+0x10/0x34 include/linux/bottom_half.h:19
---[ end trace 0000000000000000 ]---
Zero length message leads to an empty skb