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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff868cf2f0 of 88 bytes by task 29688 on cpu 0:
 prb_reserve+0x696/0xaf0 kernel/printk/printk_ringbuffer.c:1635
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2475
 hugetlb_show_meminfo_node+0xcf/0x130 mm/hugetlb.c:5260
 show_free_areas mm/show_mem.c:387 [inline]
 __show_mem+0x1302/0x1490 mm/show_mem.c:401
 warn_alloc_show_mem mm/page_alloc.c:3908 [inline]
 warn_alloc+0x189/0x1a0 mm/page_alloc.c:3933
 __vmalloc_area_node mm/vmalloc.c:3702 [inline]
 __vmalloc_node_range_noprof+0x497/0xe00 mm/vmalloc.c:3893
 __vmalloc_node_noprof mm/vmalloc.c:3956 [inline]
 vmalloc_noprof+0x82/0xc0 mm/vmalloc.c:3989
 sel_write_load+0x158/0x380 security/selinux/selinuxfs.c:593
 vfs_write+0x269/0x960 fs/read_write.c:684
 ksys_write+0xda/0x1a0 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:746
 x64_sys_call+0x27fe/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff868cf2f0 of 8 bytes by task 2983 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:486 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1874 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1922 [inline]
 _prb_read_valid+0x1c4/0x920 kernel/printk/printk_ringbuffer.c:2113
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2185
 syslog_print+0x23a/0x540 kernel/printk/printk.c:1650
 do_syslog+0x52b/0x7e0 kernel/printk/printk.c:1785
 __do_sys_syslog kernel/printk/printk.c:1877 [inline]
 __se_sys_syslog kernel/printk/printk.c:1875 [inline]
 __x64_sys_syslog+0x41/0x50 kernel/printk/printk.c:1875
 x64_sys_call+0x2f36/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:104
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000002a10 -> 0x0000000000004a10

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2983 Comm: klogd Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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