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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve_in_last

write to 0xffffffff86a7ac38 of 8 bytes by task 15392 on cpu 1:
 data_realloc kernel/printk/printk_ringbuffer.c:1228 [inline]
 prb_reserve_in_last+0x9f1/0xb30 kernel/printk/printk_ringbuffer.c:1495
 vprintk_store+0x457/0x910 kernel/printk/printk.c:2276
 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_free_areas mm/show_mem.c:383 [inline]
 __show_mem+0x10b4/0x1470 mm/show_mem.c:408
 warn_alloc_show_mem mm/page_alloc.c:4004 [inline]
 warn_alloc+0x1a1/0x1c0 mm/page_alloc.c:4030
 __vmalloc_node_range_noprof+0x2b6/0x12b0 mm/vmalloc.c:4016
 __vmalloc_node_noprof mm/vmalloc.c:4111 [inline]
 __vmalloc_noprof+0xa4/0xf0 mm/vmalloc.c:4127
 bpf_prog_alloc_no_stats+0x47/0x380 kernel/bpf/core.c:106
 bpf_prog_alloc+0x3c/0x150 kernel/bpf/core.c:153
 bpf_prog_load+0x506/0x1140 kernel/bpf/syscall.c:2992
 __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 0xffffffff86a7ac30 of 16 bytes by task 2997 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:496 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1931 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1979 [inline]
 _prb_read_valid+0x1bc/0x950 kernel/printk/printk_ringbuffer.c:2170
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2242
 syslog_print+0x109/0x560 kernel/printk/printk.c:1609
 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

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 2997 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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