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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff86d21988 of 88 bytes by task 23314 on cpu 1:
 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
 show_swap_cache_info+0x31/0x80 mm/swap_state.c:70
 show_free_areas mm/show_mem.c:398 [inline]
 __show_mem+0x135d/0x1440 mm/show_mem.c:407
 warn_alloc_show_mem mm/page_alloc.c:4021 [inline]
 warn_alloc+0x1a1/0x1c0 mm/page_alloc.c:4047
 __vmalloc_node_range_noprof+0x2b6/0x12b0 mm/vmalloc.c:4029
 __vmalloc_node_noprof mm/vmalloc.c:4124 [inline]
 __vmalloc_noprof+0xa4/0xf0 mm/vmalloc.c:4140
 bpf_prog_alloc_no_stats+0x47/0x390 kernel/bpf/core.c:107
 bpf_prog_alloc+0x3c/0x150 kernel/bpf/core.c:156
 bpf_prog_load+0x506/0x1140 kernel/bpf/syscall.c:2993
 __sys_bpf+0x505/0x7e0 kernel/bpf/syscall.c:6228
 __do_sys_bpf kernel/bpf/syscall.c:6341 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6339 [inline]
 __x64_sys_bpf+0x41/0x50 kernel/bpf/syscall.c:6339
 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 0xffffffff86d21988 of 8 bytes by task 2988 on cpu 0:
 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: 0x00000000000038fb -> 0x00000000000058fb

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 2988 Comm: klogd Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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