syzbot

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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff86cbd400 of 88 bytes by task 29996 on cpu 0:
 prb_reserve+0x6e6/0xae0 kernel/printk/printk_ringbuffer.c:1690
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x600 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
 printk_stack_address arch/x86/kernel/dumpstack.c:70 [inline]
 __show_trace_log_lvl+0x460/0x560 arch/x86/kernel/dumpstack.c:282
 __warn+0x159/0x360 kernel/panic.c:1060
 __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:2763
 reg_set_min_max+0x21c/0x260 kernel/bpf/verifier.c:17106
 check_cond_jmp_op+0x1355/0x1ab0 kernel/bpf/verifier.c:17559
 do_check_insn kernel/bpf/verifier.c:21103 [inline]
 do_check+0x4a9b/0x9860 kernel/bpf/verifier.c:21243
 do_check_common+0xd0b/0x1630 kernel/bpf/verifier.c:24581
 do_check_main kernel/bpf/verifier.c:24664 [inline]
 bpf_check+0x2f6d/0xcc10 kernel/bpf/verifier.c:25989
 bpf_prog_load+0xf76/0x1140 kernel/bpf/syscall.c:3089
 __sys_bpf+0x505/0x7e0 kernel/bpf/syscall.c:6229
 __do_sys_bpf kernel/bpf/syscall.c:6342 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6340 [inline]
 __x64_sys_bpf+0x41/0x50 kernel/bpf/syscall.c:6340
 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+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86cbd400 of 8 bytes by task 2990 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:500 [inline]
 prb_first_seq kernel/printk/printk_ringbuffer.c:2014 [inline]
 _prb_read_valid+0x383/0x950 kernel/printk/printk_ringbuffer.c:2171
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2242
 syslog_print+0x258/0x560 kernel/printk/printk.c:1628
 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+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000002660 -> 0x0000000000004660

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2990 Comm: klogd Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
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