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BUG: KCSAN: data-race in _prb_read_valid / prb_reserve

write to 0xffffffff866b2f40 of 8 bytes by task 14553 on cpu 0:
 prb_reserve+0x740/0xb60
 vprintk_store+0x53f/0x810 kernel/printk/printk.c:2301
 vprintk_emit+0x15e/0x680 kernel/printk/printk.c:2383
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2422
 vprintk+0x75/0x80 kernel/printk/printk_safe.c:68
 _printk+0x7a/0xa0 kernel/printk/printk.c:2432
 printk_stack_address arch/x86/kernel/dumpstack.c:72 [inline]
 show_trace_log_lvl+0x380/0x400 arch/x86/kernel/dumpstack.c:285
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0xf2/0x150 lib/dump_stack.c:120
 dump_stack+0x15/0x20 lib/dump_stack.c:129
 fail_dump lib/fault-inject.c:53 [inline]
 should_fail_ex+0x223/0x230 lib/fault-inject.c:154
 should_fail+0xb/0x10 lib/fault-inject.c:164
 should_fail_usercopy+0x1a/0x20 lib/fault-inject-usercopy.c:37
 _inline_copy_to_user include/linux/uaccess.h:193 [inline]
 _copy_to_user+0x20/0xa0 lib/usercopy.c:26
 copy_to_user include/linux/uaccess.h:225 [inline]
 simple_read_from_buffer+0xa0/0x110 fs/libfs.c:1124
 proc_fail_nth_read+0xf9/0x140 fs/proc/base.c:1481
 vfs_read+0x1a2/0x700 fs/read_write.c:567
 ksys_read+0xeb/0x1b0 fs/read_write.c:712
 __do_sys_read fs/read_write.c:722 [inline]
 __se_sys_read fs/read_write.c:720 [inline]
 __x64_sys_read+0x42/0x50 fs/read_write.c:720
 x64_sys_call+0x27d3/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:1
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff866b2f40 of 8 bytes by task 3006 on cpu 1:
 desc_read kernel/printk/printk_ringbuffer.c:486 [inline]
 prb_first_seq kernel/printk/printk_ringbuffer.c:1957 [inline]
 _prb_read_valid+0x3bb/0xba0 kernel/printk/printk_ringbuffer.c:2114
 prb_read_valid+0x3d/0x60 kernel/printk/printk_ringbuffer.c:2182
 syslog_print+0x157/0x760 kernel/printk/printk.c:1614
 do_syslog+0x397/0x7e0 kernel/printk/printk.c:1766
 __do_sys_syslog kernel/printk/printk.c:1858 [inline]
 __se_sys_syslog kernel/printk/printk.c:1856 [inline]
 __x64_sys_syslog+0x43/0x50 kernel/printk/printk.c:1856
 x64_sys_call+0x1677/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:104
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000000000000059c -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3006 Comm: klogd Not tainted 6.12.0-rc6-syzkaller-00077-g2e1b3cc9d7f7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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