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BUG: KCSAN: data-race in strncpy / strscpy

write to 0xffff888138f1eef0 of 8 bytes by task 12932 on cpu 0:
 strscpy+0xa9/0x170 lib/string.c:165
 strscpy_pad+0x27/0x80 lib/string_helpers.c:835
 __set_task_comm+0x46/0x140 fs/exec.c:1232
 set_task_comm include/linux/sched.h:1984 [inline]
 __kthread_create_on_node+0x2b2/0x320 kernel/kthread.c:474
 kthread_create_on_node+0x8a/0xb0 kernel/kthread.c:512
 ext4_multi_mount_protect+0x4e0/0x5c0 fs/ext4/mmp.c:374
 __ext4_fill_super fs/ext4/super.c:5270 [inline]
 ext4_fill_super+0x3057/0x43f0 fs/ext4/super.c:5637
 get_tree_bdev+0x2b1/0x3a0 fs/super.c:1294
 ext4_get_tree+0x1c/0x20 fs/ext4/super.c:5668
 vfs_get_tree+0x51/0x190 fs/super.c:1501
 do_new_mount+0x200/0x650 fs/namespace.c:3042
 path_mount+0x498/0xb40 fs/namespace.c:3372
 do_mount fs/namespace.c:3385 [inline]
 __do_sys_mount fs/namespace.c:3594 [inline]
 __se_sys_mount+0x27f/0x2d0 fs/namespace.c:3571
 __x64_sys_mount+0x67/0x80 fs/namespace.c:3571
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff888138f1eef5 of 1 bytes by task 12940 on cpu 1:
 strncpy+0xb4/0x150 lib/string.c:96
 set_cmdline kernel/trace/trace.c:2285 [inline]
 trace_save_cmdline+0x19d/0x1f0 kernel/trace/trace.c:2497
 tracing_record_taskinfo_sched_switch+0x8d/0x280 kernel/trace/trace.c:2637
 probe_sched_switch+0x80/0x90 kernel/trace/trace_sched_switch.c:35
 trace_sched_switch include/trace/events/sched.h:222 [inline]
 __schedule+0x803/0x900 kernel/sched/core.c:6619
 schedule+0x54/0x90 kernel/sched/core.c:6698
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6757
 kthread+0x12c/0x1e0 kernel/kthread.c:369
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

value changed: 0x61 -> 0x2d

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 12940 Comm: kmmpd-loop1 Not tainted 6.3.0-rc2-syzkaller-00069-g0ddc84d2dd43 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
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