GRED: Unable to relocate VQ 0x0 after dequeue, screwing up backlog
GRED: Unable to relocate VQ 0x0 after dequeue, screwing up backlog
==================================================================
BUG: KCSAN: data-race in data_push_tail / vsnprintf

write to 0xffffffff8939e2c1 of 36 bytes by task 23 on cpu 1:
 vsnprintf+0x2c0/0x8c0 lib/vsprintf.c:2896
 vscnprintf+0x41/0x90 lib/vsprintf.c:3014
 printk_sprint+0x30/0x2b0 kernel/printk/printk.c:2222
 vprintk_store+0x57b/0x910 kernel/printk/printk.c:2364
 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
 gred_dequeue+0x325/0x350 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:3446 [inline]
 neigh_hh_output include/net/neighbour.h:544 [inline]
 neigh_output include/net/neighbour.h:558 [inline]
 ip_finish_output2+0x752/0x8a0 net/ipv4/ip_output.c:236
 __ip_finish_output net/ipv4/ip_output.c:-1 [inline]
 ip_finish_output+0x112/0x290 net/ipv4/ip_output.c:324
 NF_HOOK_COND include/linux/netfilter.h:307 [inline]
 ip_output+0xbd/0x1c0 net/ipv4/ip_output.c:437
 dst_output include/net/dst.h:471 [inline]
 ip_local_out+0xaa/0xd0 net/ipv4/ip_output.c:131
 iptunnel_xmit+0x3ba/0x6b0 net/ipv4/ip_tunnel_core.c:97
 udp_tunnel_xmit_skb+0x1bf/0x220 net/ipv4/udp_tunnel_core.c:187
 send4+0x4f4/0x5e0 drivers/net/wireguard/socket.c:85
 wg_socket_send_skb_to_peer+0x94/0x130 drivers/net/wireguard/socket.c:174
 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

read to 0xffffffff8939e2e0 of 8 bytes by task 281 on cpu 0:
 data_make_reusable kernel/printk/printk_ringbuffer.c:608 [inline]
 data_push_tail+0x104/0x440 kernel/printk/printk_ringbuffer.c:693
 data_alloc+0x111/0x380 kernel/printk/printk_ringbuffer.c:1089
 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
 gred_dequeue+0x325/0x350 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:3446 [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: 0x3ffffffffffff862 -> 0x3fff000a676f676f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 281 Comm: kworker/0:2 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Workqueue: wg-crypt-wg0 wg_packet_tx_worker
==================================================================