==================================================================
BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff868801b8 of 8 bytes by task 5441 on cpu 0:
 data_alloc+0x27d/0x2b0 kernel/printk/printk_ringbuffer.c:1096
 prb_reserve+0x808/0xaf0 kernel/printk/printk_ringbuffer.c:1669
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426
 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
 __nla_validate_parse+0x1738/0x1d00 lib/nlattr.c:647
 __nla_parse+0x40/0x60 lib/nlattr.c:732
 __nlmsg_parse include/net/netlink.h:789 [inline]
 nlmsg_parse_deprecated include/net/netlink.h:830 [inline]
 rtnl_dellink+0xed/0x550 net/core/rtnetlink.c:3531
 rtnetlink_rcv_msg+0x5fb/0x6d0 net/core/rtnetlink.c:6946
 netlink_rcv_skb+0x120/0x220 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+0x5c0/0x690 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+0x145/0x180 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

read to 0xffffffff868801b8 of 8 bytes by task 5439 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:482 [inline]
 desc_push_tail kernel/printk/printk_ringbuffer.c:778 [inline]
 desc_reserve kernel/printk/printk_ringbuffer.c:924 [inline]
 prb_reserve+0x221/0xaf0 kernel/printk/printk_ringbuffer.c:1619
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426
 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
 __nla_validate_parse+0x1738/0x1d00 lib/nlattr.c:647
 __nla_parse+0x40/0x60 lib/nlattr.c:732
 __nlmsg_parse include/net/netlink.h:789 [inline]
 nlmsg_parse_deprecated include/net/netlink.h:830 [inline]
 rtnl_dellink+0xed/0x550 net/core/rtnetlink.c:3531
 rtnetlink_rcv_msg+0x5fb/0x6d0 net/core/rtnetlink.c:6946
 netlink_rcv_skb+0x120/0x220 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+0x5c0/0x690 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+0x145/0x180 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: 0x00000000000b9d98 -> 0x0000000000175d70

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 5439 Comm: syz.4.11494 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
==================================================================
netlink: 14 bytes leftover after parsing attributes in process `syz.4.11494'.