BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff868842f0 of 8 bytes by task 28637 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
 show_opcodes+0xfe/0x120 arch/x86/kernel/dumpstack.c:121
 show_iret_regs+0x12/0x40 arch/x86/kernel/dumpstack.c:147
 __show_regs+0x2a/0x440 arch/x86/kernel/process_64.c:77
 show_regs_if_on_stack arch/x86/kernel/dumpstack.c:165 [inline]
 show_trace_log_lvl+0x423/0x560 arch/x86/kernel/dumpstack.c:298
 __dump_stack+0x1d/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0xe8/0x140 lib/dump_stack.c:120
 dump_stack+0x15/0x1b lib/dump_stack.c:129
 fail_dump lib/fault-inject.c:73 [inline]
 should_fail_ex+0x265/0x280 lib/fault-inject.c:174
 should_failslab+0x8c/0xb0 mm/failslab.c:46
 slab_pre_alloc_hook mm/slub.c:4100 [inline]
 slab_alloc_node mm/slub.c:4176 [inline]
 kmem_cache_alloc_node_noprof+0x57/0x320 mm/slub.c:4248
 __alloc_skb+0x101/0x320 net/core/skbuff.c:658
 alloc_skb include/linux/skbuff.h:1340 [inline]
 nlmsg_new include/net/netlink.h:1019 [inline]
 audit_buffer_alloc kernel/audit.c:1795 [inline]
 audit_log_start+0x380/0x6c0 kernel/audit.c:1913
 audit_seccomp+0x48/0x100 kernel/auditsc.c:3001
 seccomp_log kernel/seccomp.c:1033 [inline]
 __seccomp_filter+0x69d/0x10d0 kernel/seccomp.c:1328
 __secure_computing+0x82/0x150 kernel/seccomp.c:1388
 syscall_trace_enter+0xcf/0x1e0 kernel/entry/common.c:52
 syscall_enter_from_user_mode_work include/linux/entry-common.h:170 [inline]
 syscall_enter_from_user_mode include/linux/entry-common.h:200 [inline]
 do_syscall_64+0xac/0x200 arch/x86/entry/syscall_64.c:90
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff868842f0 of 8 bytes by task 28625 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
 selinux_netlink_send+0x583/0x5f0 security/selinux/hooks.c:6155
 security_netlink_send+0x40/0x80 security/security.c:4483
 netlink_sendmsg+0x498/0x6b0 net/netlink/af_netlink.c:1873
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg+0x145/0x180 net/socket.c:727
 ____sys_sendmsg+0x345/0x4e0 net/socket.c:2566
 ___sys_sendmsg+0x17b/0x1d0 net/socket.c:2620
 __sys_sendmmsg+0x178/0x300 net/socket.c:2709
 __do_sys_sendmmsg net/socket.c:2736 [inline]
 __se_sys_sendmmsg net/socket.c:2733 [inline]
 __x64_sys_sendmmsg+0x57/0x70 net/socket.c:2733
 x64_sys_call+0x2f2f/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:308
 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: 0x0000000000019610 -> 0x00000000000c15d0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 28625 Comm: syz.2.5166 Not tainted 6.15.0-syzkaller-03645-g3d413f0cfd7e #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=12 sclass=netlink_route_socket pid=28625 comm=syz.2.5166