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BUG: KCSAN: data-race in do_syslog / log_store

write to 0xffffffff89513200 of 8 bytes by task 11223 on cpu 1:
 log_store+0x7a2/0x7d0 kernel/printk/printk.c:672
 log_output kernel/printk/printk.c:1932 [inline]
 vprintk_store+0x5ba/0x700 kernel/printk/printk.c:1983
 vprintk_emit+0x114/0x4f0 kernel/printk/printk.c:2011
 vprintk_default+0x24/0x30 kernel/printk/printk.c:2047
 vprintk_func+0x13d/0x140 kernel/printk/printk_safe.c:393
 printk+0x62/0x82 kernel/printk/printk.c:2078
 br_set_state+0x159/0x290 net/bridge/br_stp.c:51
 br_stp_disable_port+0x58/0x130 net/bridge/br_stp_if.c:106
 del_nbp+0xc6/0x7b0 net/bridge/br_if.c:333
 br_dev_delete+0x5b/0xe0 net/bridge/br_if.c:375
 default_device_exit_batch+0x1ae/0x3e0 net/core/dev.c:10907
 ops_exit_list net/core/net_namespace.c:189 [inline]
 cleanup_net+0x4dc/0x8c0 net/core/net_namespace.c:603
 process_one_work+0x3e1/0x9a0 kernel/workqueue.c:2269
 worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
 kthread+0x20d/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffffffff89513200 of 8 bytes by task 8304 on cpu 0:
 do_syslog+0x2e4/0x1480 kernel/printk/printk.c:1561
 kmsg_read+0x7a/0xa0 fs/proc/kmsg.c:40
 pde_read fs/proc/inode.c:306 [inline]
 proc_reg_read+0xde/0x1a0 fs/proc/inode.c:316
 vfs_read+0x16d/0x5e0 fs/read_write.c:479
 ksys_read+0xce/0x180 fs/read_write.c:607
 __do_sys_read fs/read_write.c:617 [inline]
 __se_sys_read fs/read_write.c:615 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:615
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8304 Comm: in:imklog Not tainted 5.9.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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