================================================================== BUG: KCSAN: data-race in data_alloc / prb_reserve write to 0xffffffff8687bfa0 of 8 bytes by task 3627 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 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:12598 netdev_info+0x9b/0xd0 net/core/dev.c:12653 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:3236 [inline] process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3319 worker_thread+0x582/0x770 kernel/workqueue.c:3400 kthread+0x486/0x510 kernel/kthread.c:463 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 read to 0xffffffff8687bfa0 of 8 bytes by task 25828 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 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 dump_header+0x81/0x220 mm/oom_kill.c:467 oom_kill_process+0x342/0x400 mm/oom_kill.c:1040 out_of_memory+0x979/0xb80 mm/oom_kill.c:1178 mem_cgroup_out_of_memory mm/memcontrol.c:1649 [inline] mem_cgroup_oom mm/memcontrol.c:1672 [inline] try_charge_memcg+0x5e6/0x9e0 mm/memcontrol.c:2399 try_charge mm/memcontrol.c:2499 [inline] charge_memcg+0x51/0xc0 mm/memcontrol.c:4702 mem_cgroup_swapin_charge_folio+0xcc/0x150 mm/memcontrol.c:4788 __read_swap_cache_async+0x1df/0x350 mm/swap_state.c:441 swap_cluster_readahead+0x376/0x3e0 mm/swap_state.c:632 swapin_readahead+0xde/0x6f0 mm/swap_state.c:811 do_swap_page+0x301/0x2430 mm/memory.c:4586 handle_pte_fault mm/memory.c:6055 [inline] __handle_mm_fault mm/memory.c:6195 [inline] handle_mm_fault+0x9a5/0x2c20 mm/memory.c:6364 do_user_addr_fault+0x636/0x1090 arch/x86/mm/fault.c:1336 handle_page_fault arch/x86/mm/fault.c:1476 [inline] exc_page_fault+0x62/0xa0 arch/x86/mm/fault.c:1532 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623 value changed: 0x0000000000008be0 -> 0x00000000000b0a20 Reported by Kernel Concurrency Sanitizer on: CPU: 1 UID: 0 PID: 25828 Comm: syz.4.8338 Tainted: G W syzkaller #0 PREEMPT(voluntary) Tainted: [W]=WARN Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 ================================================================== do_swap_page+0x301/0x2430 mm/memory.c:4586 handle_pte_fault mm/memory.c:6055 [inline] __handle_mm_fault mm/memory.c:6195 [inline] handle_mm_fault+0x9a5/0x2c20 mm/memory.c:6364 do_user_addr_fault+0x636/0x1090 arch/x86/mm/fault.c:1336 handle_page_fault arch/x86/mm/fault.c:1476 [inline] exc_page_fault+0x62/0xa0 arch/x86/mm/fault.c:1532 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623 RIP: 0033:0x7f752597560c Code: 66 0f 1f 44 00 00 69 3d a6 00 e9 00 e8 03 00 00 48 8d 1d a7 09 36 00 e8 42 95 12 00 eb 0c 48 81 c3 f0 00 00 00 48 39 eb 74 24 <80> 7b 20 00 74 ee 8b 43 0c 85 c0 74 e7 48 89 df 48 81 c3 f0 00 00 RSP: 002b:00007ffe50887970 EFLAGS: 00010287 RAX: 0000000000000000 RBX: 00007f7525cd6090 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000055558bec1808 RBP: 00007f7525cd7da0 R08: 0000000000000000 R09: 7fffffffffffffff R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000091a4d R13: 00007f7525cd6090 R14: ffffffffffffffff R15: 00007ffe50887a80 memory: usage 307200kB, limit 307200kB, failcnt 5877 memory+swap: usage 307704kB, limit 9007199254740988kB, failcnt 0 kmem: usage 307200kB, limit 9007199254740988kB, failcnt 0 Memory cgroup stats for /syz4: cache 0 rss 0 shmem 0 mapped_file 0 dirty 0 writeback 0 workingset_refault_anon 52938 workingset_refault_file 13851 swap 516096 swapcached 0 pgpgin 836846 pgpgout 836846 pgfault 926874 pgmajfault 8050 inactive_anon 0 active_anon 0 inactive_file 0 active_file 0 unevictable 0 hierarchical_memory_limit 314572800 hierarchical_memsw_limit 9223372036854771712 total_cache 0 total_rss 0 total_shmem 0 total_mapped_file 0 total_dirty 0 total_writeback 0 total_workingset_refault_anon 52938 total_workingset_refault_file 13851 total_swap 516096 total_swapcached 0 total_pgpgin 836846 total_pgpgout 836846 total_pgfault 926874 total_pgmajfault 8050 total_inactive_anon 0 total_active_anon 0 total_inactive_file 0 total_active_file 0 total_unevictable 0 oom-kill:constraint=CONSTRAINT_MEMCG,nodemask=(null),cpuset=/,mems_allowed=0,oom_memcg=/syz4,task_memcg=/syz4,task=syz.4.8338,pid=25828,uid=0 Memory cgroup out of memory: Killed process 25828 (syz.4.8338) total-vm:93828kB, anon-rss:1004kB, file-rss:22440kB, shmem-rss:0kB, UID:0 pgtables:128kB oom_score_adj:1000