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BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff86e702f8 of 8 bytes by interrupt on cpu 0:
 data_alloc+0x308/0x380 kernel/printk/printk_ringbuffer.c:1130
 prb_reserve+0x8e3/0xaf0 kernel/printk/printk_ringbuffer.c:1727
 vprintk_store+0x54e/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x610 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
 lapbeth_xmit+0x1bd/0x1c0 drivers/net/wan/lapbether.c:-1
 __netdev_start_xmit include/linux/netdevice.h:5432 [inline]
 netdev_start_xmit include/linux/netdevice.h:5441 [inline]
 xmit_one net/core/dev.c:3953 [inline]
 dev_hard_start_xmit+0x10c/0x380 net/core/dev.c:3969
 __dev_queue_xmit+0xbfd/0x1ec0 net/core/dev.c:4958
 dev_queue_xmit include/linux/netdevice.h:3464 [inline]
 x25_send_frame+0xfe/0x130 net/x25/x25_dev.c:193
 x25_transmit_restart_confirmation net/x25/x25_link.c:178 [inline]
 x25_link_control+0x3d1/0x500 net/x25/x25_link.c:-1
 x25_receive_data net/x25/x25_dev.c:43 [inline]
 x25_lapb_receive_frame+0x2d6/0x770 net/x25/x25_dev.c:127
 __netif_receive_skb_one_core net/core/dev.c:6297 [inline]
 netif_receive_skb_core+0x122/0x130 net/core/dev.c:6322
 lapbeth_napi_poll+0x42/0x90 drivers/net/wan/lapbether.c:100
 __napi_poll+0x61/0x300 net/core/dev.c:7830
 napi_poll net/core/dev.c:7893 [inline]
 net_rx_action+0x456/0x930 net/core/dev.c:8050
 handle_softirqs+0xcc/0x2a0 kernel/softirq.c:645
 __do_softirq kernel/softirq.c:679 [inline]
 invoke_softirq kernel/softirq.c:519 [inline]
 __irq_exit_rcu+0x44/0xe0 kernel/softirq.c:758
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0x74/0x80 arch/x86/kernel/apic/apic.c:1062
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
 __preempt_count_dec_and_test arch/x86/include/asm/preempt.h:123 [inline]
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:211 [inline]
 _raw_spin_unlock_irqrestore+0x1a/0x30 kernel/locking/spinlock.c:221
 class_raw_spinlock_irqsave_destructor include/linux/spinlock.h:596 [inline]
 try_to_wake_up+0x4ba/0x6d0 kernel/sched/core.c:4315
 __mutex_unlock_slowpath+0x217/0x370 kernel/locking/mutex.c:1077
 mutex_unlock+0x81/0x90 kernel/locking/mutex.c:582
 __rtnl_unlock+0x56/0xb0 net/core/rtnetlink.c:143
 netdev_run_todo+0xb6/0x9d0 net/core/dev.c:11819
 rtnl_unlock+0xe/0x20 net/core/rtnetlink.c:157
 linkwatch_event+0x45/0x50 net/core/link_watch.c:315
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0x56a/0xa50 kernel/workqueue.c:3479
 worker_thread+0x569/0x750 kernel/workqueue.c:3560
 kthread+0x223/0x270 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 0xffffffff86e702f8 of 8 bytes by task 10203 on cpu 1:
 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+0x54e/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x610 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
 ib_get_eth_speed+0x3c8/0x560 drivers/infiniband/core/verbs.c:2073
 rxe_query_port+0x7d/0x220 drivers/infiniband/sw/rxe/rxe_verbs.c:56
 __ib_query_port drivers/infiniband/core/device.c:2304 [inline]
 ib_query_port+0x122/0x3d0 drivers/infiniband/core/device.c:2336
 ib_setup_port_attrs+0x13e/0x1480 drivers/infiniband/core/sysfs.c:1384
 add_one_compat_dev+0x297/0x390 drivers/infiniband/core/device.c:1002
 rdma_dev_init_net+0x1b9/0x240 drivers/infiniband/core/device.c:1227
 ops_init+0x22a/0x2e0 net/core/net_namespace.c:137
 setup_net+0x9f/0x230 net/core/net_namespace.c:443
 copy_net_ns+0x333/0x490 net/core/net_namespace.c:582
 create_new_namespaces+0x1f6/0x420 kernel/nsproxy.c:132
 unshare_nsproxy_namespaces+0x115/0x150 kernel/nsproxy.c:234
 ksys_unshare+0x42b/0x710 kernel/fork.c:3297
 __do_sys_unshare kernel/fork.c:3361 [inline]
 __se_sys_unshare kernel/fork.c:3359 [inline]
 __x64_sys_unshare+0x1f/0x30 kernel/fork.c:3359
 x64_sys_call+0x1e33/0x2550 arch/x86/include/generated/asm/syscalls_64.h:273
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000001ce868 -> 0x00000000002427b0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 10203 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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lo speed is unknown, defaulting to 1000