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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff86cb42b0 of 88 bytes by task 30144 on cpu 0:
 prb_reserve+0x6fb/0xaf0 kernel/printk/printk_ringbuffer.c:1693
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
 dev_vprintk_emit+0x242/0x2a0 drivers/base/core.c:4996
 dev_printk_emit+0x84/0xb0 drivers/base/core.c:5007
 __netdev_printk+0x34b/0x370 net/core/dev.c:12964
 netdev_warn+0xa6/0xd0 net/core/dev.c:13017
 ieee802154_subif_start_xmit+0xd7/0x100 net/mac802154/tx.c:232
 __netdev_start_xmit include/linux/netdevice.h:5400 [inline]
 netdev_start_xmit include/linux/netdevice.h:5409 [inline]
 xmit_one net/core/dev.c:3889 [inline]
 dev_hard_start_xmit+0x10c/0x380 net/core/dev.c:3905
 sch_direct_xmit+0x199/0x580 net/sched/sch_generic.c:372
 __dev_xmit_skb net/core/dev.c:4214 [inline]
 __dev_queue_xmit+0xda4/0x1e90 net/core/dev.c:4836
 dev_queue_xmit include/linux/netdevice.h:3446 [inline]
 __bpf_tx_skb net/core/filter.c:2156 [inline]
 __bpf_redirect_common net/core/filter.c:2200 [inline]
 __bpf_redirect+0x83a/0x960 net/core/filter.c:2207
 ____bpf_clone_redirect net/core/filter.c:2497 [inline]
 bpf_clone_redirect+0x206/0x280 net/core/filter.c:2460
 bpf_prog_43388ee67a65acbd+0x22/0x2a
 bpf_dispatcher_nop_func include/linux/bpf.h:1454 [inline]
 __bpf_prog_run include/linux/filter.h:724 [inline]
 bpf_prog_run include/linux/filter.h:731 [inline]
 bpf_test_run+0x298/0x620 net/bpf/test_run.c:422
 bpf_prog_test_run_skb+0xe67/0x11b0 net/bpf/test_run.c:1225
 bpf_prog_test_run+0x208/0x340 kernel/bpf/syscall.c:4859
 __sys_bpf+0x8da/0xc30 kernel/bpf/syscall.c:6436
 __do_sys_bpf kernel/bpf/syscall.c:6537 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6534 [inline]
 __x64_sys_bpf+0x69/0x80 kernel/bpf/syscall.c:6534
 x64_sys_call+0x10cb/0x3020 arch/x86/include/generated/asm/syscalls_64.h:322
 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 0xffffffff86cb42b0 of 8 bytes by task 2970 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:500 [inline]
 prb_first_seq kernel/printk/printk_ringbuffer.c:2017 [inline]
 _prb_read_valid+0x325/0x930 kernel/printk/printk_ringbuffer.c:2174
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2245
 syslog_print+0x109/0x560 kernel/printk/printk.c:1612
 do_syslog+0x52b/0x7f0 kernel/printk/printk.c:1763
 __do_sys_syslog kernel/printk/printk.c:1855 [inline]
 __se_sys_syslog kernel/printk/printk.c:1853 [inline]
 __x64_sys_syslog+0x41/0x50 kernel/printk/printk.c:1853
 x64_sys_call+0x2b9e/0x3020 arch/x86/include/generated/asm/syscalls_64.h:104
 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

value changed: 0x00000000000025cc -> 0x00000000000045cc

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2970 Comm: klogd Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
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