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BUG: KCSAN: data-race in do_syslog / log_store

write to 0xffffffff89514200 of 8 bytes by task 3952 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_make_forwarding+0xbc/0x150 net/bridge/br_stp.c:435
 br_port_state_selection+0x127/0x330 net/bridge/br_stp.c:463
 br_stp_enable_port+0xcb/0x110 net/bridge/br_stp_if.c:94
 br_port_carrier_check+0x2f4/0x330 net/bridge/br_if.c:80
 br_device_event+0x2a7/0x520 net/bridge/br.c:86
 notifier_call_chain kernel/notifier.c:83 [inline]
 __raw_notifier_call_chain kernel/notifier.c:361 [inline]
 raw_notifier_call_chain+0x53/0xb0 kernel/notifier.c:368
 call_netdevice_notifiers_info net/core/dev.c:2033 [inline]
 netdev_state_change+0xe8/0x160 net/core/dev.c:1463
 linkwatch_do_dev+0x224/0x250 net/core/link_watch.c:167
 __linkwatch_run_queue+0x511/0x740 net/core/link_watch.c:212
 linkwatch_event+0x3c/0x50 net/core/link_watch.c:251
 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 0xffffffff89514200 of 8 bytes by task 8341 on cpu 0:
 do_syslog+0x3b2/0x1480 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:615
 __do_sys_read fs/read_write.c:625 [inline]
 __se_sys_read fs/read_write.c:623 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:623
 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: 8341 Comm: in:imklog Not tainted 5.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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