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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff86abc750 of 88 bytes by task 4579 on cpu 1:
 prb_reserve+0x6e6/0xae0 kernel/printk/printk_ringbuffer.c:1690
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2302
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2402
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2441
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2451
 __show_regs+0x85/0x420 arch/x86/kernel/process_64.c:85
 show_regs_if_on_stack arch/x86/kernel/dumpstack.c:165 [inline]
 __show_trace_log_lvl+0x38f/0x560 arch/x86/kernel/dumpstack.c:298
 __warn+0x159/0x350 kernel/panic.c:899
 __report_bug+0x241/0x490 lib/bug.c:249
 report_bug_entry+0xb2/0x100 lib/bug.c:269
 handle_bug+0xca/0x200 arch/x86/kernel/traps.c:430
 exc_invalid_op+0x1a/0x50 arch/x86/kernel/traps.c:489
 asm_exc_invalid_op+0x1a/0x20 arch/x86/include/asm/idtentry.h:616
 reg_bounds_sanity_check+0x27d/0x660 kernel/bpf/verifier.c:2742
 reg_set_min_max+0x21c/0x260 kernel/bpf/verifier.c:16577
 check_cond_jmp_op+0x13bd/0x1a80 kernel/bpf/verifier.c:17010
 do_check_insn kernel/bpf/verifier.c:20446 [inline]
 do_check+0x3356/0x8250 kernel/bpf/verifier.c:20586
 do_check_common+0xccf/0x1300 kernel/bpf/verifier.c:23870
 do_check_main kernel/bpf/verifier.c:23953 [inline]
 bpf_check+0x2f85/0xc890 kernel/bpf/verifier.c:25260
 bpf_prog_load+0xf76/0x1140 kernel/bpf/syscall.c:3088
 __sys_bpf+0x469/0x7b0 kernel/bpf/syscall.c:6164
 __do_sys_bpf kernel/bpf/syscall.c:6274 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6272 [inline]
 __x64_sys_bpf+0x41/0x50 kernel/bpf/syscall.c:6272
 x64_sys_call+0x28e1/0x3000 arch/x86/include/generated/asm/syscalls_64.h:322
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86abc750 of 8 bytes by task 2994 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:500 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1931 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1979 [inline]
 _prb_read_valid+0x1c4/0x950 kernel/printk/printk_ringbuffer.c:2170
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2242
 syslog_print+0x258/0x560 kernel/printk/printk.c:1626
 do_syslog+0x52b/0x7f0 kernel/printk/printk.c:1761
 __do_sys_syslog kernel/printk/printk.c:1853 [inline]
 __se_sys_syslog kernel/printk/printk.c:1851 [inline]
 __x64_sys_syslog+0x41/0x50 kernel/printk/printk.c:1851
 x64_sys_call+0x27ce/0x3000 arch/x86/include/generated/asm/syscalls_64.h:104
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000000000000a698 -> 0x000000000000c698

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 2994 Comm: klogd Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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