syzbot

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BUG: KCSAN: data-race in __lookup_mnt / umount_tree

write to 0xffff88813a866b98 of 8 bytes by task 7201 on cpu 0:
 unhash_mnt fs/namespace.c:884 [inline]
 umount_mnt fs/namespace.c:898 [inline]
 umount_tree+0x59b/0x8d0 fs/namespace.c:1594
 path_umount+0x99b/0xa10 fs/namespace.c:1802
 ksys_umount fs/namespace.c:1825 [inline]
 __do_sys_umount fs/namespace.c:1830 [inline]
 __se_sys_umount fs/namespace.c:1828 [inline]
 __x64_sys_umount+0xb5/0xe0 fs/namespace.c:1828
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff88813a866b98 of 8 bytes by task 7202 on cpu 1:
 __lookup_mnt+0xa9/0xf0 fs/namespace.c:674
 __follow_mount_rcu fs/namei.c:1501 [inline]
 handle_mounts fs/namei.c:1531 [inline]
 step_into+0x3f6/0x7d0 fs/namei.c:1831
 walk_component+0x164/0x230 fs/namei.c:1999
 lookup_last fs/namei.c:2450 [inline]
 path_lookupat+0x11d/0x2b0 fs/namei.c:2474
 filename_lookup+0x133/0x310 fs/namei.c:2503
 user_path_at_empty+0x3e/0x110 fs/namei.c:2876
 user_path_at include/linux/namei.h:57 [inline]
 do_mount fs/namespace.c:3380 [inline]
 __do_sys_mount fs/namespace.c:3591 [inline]
 __se_sys_mount+0x24d/0x2d0 fs/namespace.c:3568
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3568
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0xffff888136e49600 -> 0xffff888136deb6c0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7202 Comm: syz-executor.5 Not tainted 6.0.0-rc4-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022
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