CPU: 0 UID: 0 PID: 12293 Comm: syz.5.2925 Tainted: G W syzkaller #0 PREEMPT(voluntary) Tainted: [W]=WARN Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025 Call Trace: ================================================================== BUG: KCSAN: data-race in data_alloc / prb_reserve write to 0xffffffff86874340 of 8 bytes by task 12 on cpu 1: data_alloc+0x280/0x2e0 kernel/printk/printk_ringbuffer.c:1102 prb_reserve+0x807/0xaf0 kernel/printk/printk_ringbuffer.c:1685 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2299 vprintk_emit+0x10d/0x580 kernel/printk/printk.c:2399 dev_vprintk_emit+0x242/0x2a0 drivers/base/core.c:4914 dev_printk_emit+0x84/0xb0 drivers/base/core.c:4925 __netdev_printk+0x35c/0x3e0 net/core/dev.c:12716 netdev_info+0x9b/0xd0 net/core/dev.c:12771 nsim_udp_tunnel_set_port+0x13b/0x160 drivers/net/netdevsim/udp_tunnels.c:31 udp_tunnel_nic_device_sync_one net/ipv4/udp_tunnel_nic.c:-1 [inline] udp_tunnel_nic_device_sync_by_port net/ipv4/udp_tunnel_nic.c:249 [inline] __udp_tunnel_nic_device_sync+0x567/0x9c0 net/ipv4/udp_tunnel_nic.c:292 udp_tunnel_nic_device_sync_work+0x5d/0x5f0 net/ipv4/udp_tunnel_nic.c:740 process_one_work kernel/workqueue.c:3263 [inline] process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3346 worker_thread+0x582/0x770 kernel/workqueue.c:3427 kthread+0x489/0x510 kernel/kthread.c:463 ret_from_fork+0x122/0x1b0 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 read to 0xffffffff86874340 of 8 bytes by task 12293 on cpu 0: desc_read kernel/printk/printk_ringbuffer.c:479 [inline] desc_push_tail kernel/printk/printk_ringbuffer.c:775 [inline] desc_reserve kernel/printk/printk_ringbuffer.c:921 [inline] prb_reserve+0x220/0xaf0 kernel/printk/printk_ringbuffer.c:1635 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2299 vprintk_emit+0x10d/0x580 kernel/printk/printk.c:2399 vprintk_default+0x26/0x30 kernel/printk/printk.c:2438 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82 _printk+0x79/0xa0 kernel/printk/printk.c:2448 printk_stack_address arch/x86/kernel/dumpstack.c:70 [inline] show_trace_log_lvl+0x4e3/0x560 arch/x86/kernel/dumpstack.c:282 __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:4931 [inline] slab_alloc_node mm/slub.c:5264 [inline] kmem_cache_alloc_noprof+0x50/0x480 mm/slub.c:5295 audit_buffer_alloc kernel/audit.c:1830 [inline] audit_log_start+0x342/0x720 kernel/audit.c:1955 audit_seccomp+0x48/0x100 kernel/auditsc.c:2976 seccomp_log kernel/seccomp.c:1048 [inline] __seccomp_filter+0x83e/0x1250 kernel/seccomp.c:1344 __secure_computing+0x82/0x150 kernel/seccomp.c:1404 syscall_trace_enter+0xcf/0x1e0 kernel/entry/syscall-common.c:44 syscall_enter_from_user_mode_work include/linux/entry-common.h:95 [inline] syscall_enter_from_user_mode include/linux/entry-common.h:125 [inline] do_syscall_64+0xac/0x200 arch/x86/entry/syscall_64.c:90 entry_SYSCALL_64_after_hwframe+0x77/0x7f value changed: 0xfffffffffffe4428 -> 0x0000000000083d78 Reported by Kernel Concurrency Sanitizer on: CPU: 0 UID: 0 PID: 12293 Comm: syz.5.2925 Tainted: G W syzkaller #0 PREEMPT(voluntary) Tainted: [W]=WARN Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025 ================================================================== __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:4931 [inline] slab_alloc_node mm/slub.c:5264 [inline] kmem_cache_alloc_noprof+0x50/0x480 mm/slub.c:5295 audit_buffer_alloc kernel/audit.c:1830 [inline] audit_log_start+0x342/0x720 kernel/audit.c:1955 audit_seccomp+0x48/0x100 kernel/auditsc.c:2976 seccomp_log kernel/seccomp.c:1048 [inline] __seccomp_filter+0x83e/0x1250 kernel/seccomp.c:1344 __secure_computing+0x82/0x150 kernel/seccomp.c:1404 syscall_trace_enter+0xcf/0x1e0 kernel/entry/syscall-common.c:44 syscall_enter_from_user_mode_work include/linux/entry-common.h:95 [inline] syscall_enter_from_user_mode include/linux/entry-common.h:125 [inline] do_syscall_64+0xac/0x200 arch/x86/entry/syscall_64.c:90 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f6b3991f749 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f6b3837f038 EFLAGS: 00000246 ORIG_RAX: 00000000000000ac RAX: ffffffffffffffda RBX: 00007f6b39b75fa0 RCX: 00007f6b3991f749 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 00007f6b3837f090 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 00007f6b39b76038 R14: 00007f6b39b75fa0 R15: 00007ffcf8079398