netlink: 'syz.4.2233': attribute type 21 has an invalid length.
==================================================================
BUG: KCSAN: data-race in console_flush_all / console_flush_all

write to 0xffffffff86a1f7c8 of 8 bytes by task 8519 on cpu 0:
 console_emit_next_record kernel/printk/printk.c:3099 [inline]
 console_flush_all+0x35a/0x730 kernel/printk/printk.c:3226
 __console_flush_and_unlock kernel/printk/printk.c:3285 [inline]
 console_unlock+0xa1/0x330 kernel/printk/printk.c:3325
 vprintk_emit+0x388/0x650 kernel/printk/printk.c:2450
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2475
 __netdev_printk+0x321/0x3e0 net/core/dev.c:12596
 netdev_printk+0x96/0xc0 net/core/dev.c:12614
 ppp_send_frame drivers/net/ppp/ppp_generic.c:1774 [inline]
 __ppp_xmit_process+0xb30/0xe40 drivers/net/ppp/ppp_generic.c:1658
 ppp_xmit_process+0x7d/0x120 drivers/net/ppp/ppp_generic.c:1683
 ppp_write+0x297/0x310 drivers/net/ppp/ppp_generic.c:540
 vfs_write+0x266/0x8e0 fs/read_write.c:684
 ksys_write+0xda/0x1a0 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:746
 x64_sys_call+0x27fe/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86a1f7c8 of 8 bytes by task 8521 on cpu 1:
 console_flush_all+0x563/0x730 kernel/printk/printk.c:3227
 __console_flush_and_unlock kernel/printk/printk.c:3285 [inline]
 console_unlock+0xa1/0x330 kernel/printk/printk.c:3325
 vprintk_emit+0x388/0x650 kernel/printk/printk.c:2450
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2475
 validate_nla lib/nlattr.c:414 [inline]
 __nla_validate_parse+0x1227/0x1d00 lib/nlattr.c:635
 __nla_validate+0x40/0x60 lib/nlattr.c:677
 nlmsg_validate_deprecated include/net/netlink.h:931 [inline]
 rtm_to_fib_config+0x79/0x950 net/ipv4/fib_frontend.c:742
 inet_rtm_newroute+0x75/0x140 net/ipv4/fib_frontend.c:917
 rtnetlink_rcv_msg+0x5fb/0x6d0 net/core/rtnetlink.c:6946
 netlink_rcv_skb+0x123/0x220 net/netlink/af_netlink.c:2552
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6973
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x5bd/0x690 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x58b/0x6b0 net/netlink/af_netlink.c:1896
 sock_sendmsg_nosec net/socket.c:714 [inline]
 __sock_sendmsg+0x142/0x180 net/socket.c:729
 ____sys_sendmsg+0x31e/0x4e0 net/socket.c:2614
 ___sys_sendmsg+0x17b/0x1d0 net/socket.c:2668
 __sys_sendmsg net/socket.c:2700 [inline]
 __do_sys_sendmsg net/socket.c:2705 [inline]
 __se_sys_sendmsg net/socket.c:2703 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2703
 x64_sys_call+0x191e/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000b25 -> 0x0000000000000b26

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 8521 Comm: syz.4.2233 Not tainted 6.16.0-syzkaller-10910-g0905809b38bd #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================
netlink: 'syz.4.2233': attribute type 1 has an invalid length.