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BUG: KCSAN: data-race in do_syslog / do_syslog

write to 0xffffffff84530510 of 8 bytes by task 1614 on cpu 1:
 syslog_print kernel/printk/printk.c:1463 [inline]
 do_syslog+0xf87/0x1160 kernel/printk/printk.c:1588
 kmsg_read+0x7a/0xa0 fs/proc/kmsg.c:40
 pde_read fs/proc/inode.c:321 [inline]
 proc_reg_read+0xe1/0x1b0 fs/proc/inode.c:331
 vfs_read+0x154/0x5d0 fs/read_write.c:494
 ksys_read+0xce/0x180 fs/read_write.c:634
 __do_sys_read fs/read_write.c:644 [inline]
 __se_sys_read fs/read_write.c:642 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:642
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffffffff84530510 of 8 bytes by task 3196 on cpu 0:
 do_syslog+0xc88/0x1160 kernel/printk/printk.c:1584
 __do_sys_syslog kernel/printk/printk.c:1680 [inline]
 __se_sys_syslog kernel/printk/printk.c:1678 [inline]
 __x64_sys_syslog+0x3f/0x50 kernel/printk/printk.c:1678
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 3196 Comm: syz-executor.3 Not tainted 5.12.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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