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

write to 0xffffffff86c90228 of 8 bytes by task 17613 on cpu 1:
 data_alloc+0x308/0x380 kernel/printk/printk_ringbuffer.c:1130
 prb_reserve+0x8e3/0xaf0 kernel/printk/printk_ringbuffer.c:1727
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2504
 __show_regs+0xbb/0x430 arch/x86/kernel/process_64.c:89
 show_regs_if_on_stack arch/x86/kernel/dumpstack.c:165 [inline]
 __show_trace_log_lvl+0x38f/0x560 arch/x86/kernel/dumpstack.c:298
 __dump_stack+0x1d/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x95/0xd0 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+0x25e/0x270 lib/fault-inject.c:174
 should_fail+0xb/0x20 lib/fault-inject.c:184
 should_fail_usercopy+0x1a/0x20 lib/fault-inject-usercopy.c:35
 _inline_copy_from_user include/linux/uaccess.h:170 [inline]
 _copy_from_user+0x1c/0xb0 lib/usercopy.c:18
 copy_from_user include/linux/uaccess.h:222 [inline]
 kstrtoul_from_user+0x69/0xf0 lib/kstrtox.c:435
 tracing_entries_write+0x7a/0x1e0 kernel/trace/trace.c:5729
 vfs_write+0x252/0x990 fs/read_write.c:685
 ksys_write+0xdc/0x1a0 fs/read_write.c:739
 __do_sys_write fs/read_write.c:750 [inline]
 __se_sys_write fs/read_write.c:747 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:747
 x64_sys_call+0x27e1/0x3020 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86c90228 of 8 bytes by task 6870 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:496 [inline]
 desc_push_tail kernel/printk/printk_ringbuffer.c:792 [inline]
 desc_reserve kernel/printk/printk_ringbuffer.c:938 [inline]
 prb_reserve+0x21a/0xaf0 kernel/printk/printk_ringbuffer.c:1677
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
 vprintk_deferred kernel/printk/printk.c:4714 [inline]
 _printk_deferred+0x82/0xb0 kernel/printk/printk.c:4723
 ___ratelimit+0x42f/0x450 lib/ratelimit.c:86
 net_ratelimit+0x1c/0x30 net/core/utils.c:41
 gred_dequeue+0x28a/0x350 net/sched/sch_gred.c:273
 dequeue_skb net/sched/sch_generic.c:322 [inline]
 qdisc_restart net/sched/sch_generic.c:427 [inline]
 __qdisc_run+0x18b/0xc60 net/sched/sch_generic.c:445
 qdisc_run include/net/pkt_sched.h:120 [inline]
 __dev_xmit_skb net/core/dev.c:4297 [inline]
 __dev_queue_xmit+0x11df/0x1e90 net/core/dev.c:4836
 dev_queue_xmit include/linux/netdevice.h:3448 [inline]
 neigh_hh_output include/net/neighbour.h:544 [inline]
 neigh_output include/net/neighbour.h:558 [inline]
 ip6_finish_output2+0x865/0xd70 net/ipv6/ip6_output.c:136
 __ip6_finish_output net/ipv6/ip6_output.c:-1 [inline]
 ip6_finish_output+0x1e1/0x410 net/ipv6/ip6_output.c:219
 NF_HOOK_COND include/linux/netfilter.h:307 [inline]
 ip6_output+0x10a/0x280 net/ipv6/ip6_output.c:246
 dst_output include/net/dst.h:471 [inline]
 ip6_local_out+0x77/0xd0 net/ipv6/output_core.c:128
 ip6tunnel_xmit include/net/ip6_tunnel.h:174 [inline]
 udp_tunnel6_xmit_skb+0x3f9/0x730 net/ipv6/ip6_udp_tunnel.c:112
 send6+0x36c/0x490 drivers/net/wireguard/socket.c:151
 wg_socket_send_skb_to_peer+0xc0/0x130 drivers/net/wireguard/socket.c:177
 wg_packet_create_data_done drivers/net/wireguard/send.c:251 [inline]
 wg_packet_tx_worker+0x12d/0x340 drivers/net/wireguard/send.c:276
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0x4d4/0x9a0 kernel/workqueue.c:3405
 worker_thread+0x569/0x750 kernel/workqueue.c:3486
 kthread+0x221/0x270 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x000000000007e8f0 -> 0x000000000012bbc8

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 6870 Comm: kworker/0:9 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: wg-crypt-wg0 wg_packet_tx_worker
==================================================================
net_ratelimit: 2 callbacks suppressed
GRED: Unable to relocate VQ 0x0 after dequeue, screwing up backlog