syzbot

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BUG: KCSAN: data-race in inode_permission / kernfs_refresh_inode

read to 0xffff8881254973e0 of 4 bytes by task 8000 on cpu 1:
 HAS_UNMAPPED_ID include/linux/fs.h:2049 [inline]
 inode_permission+0x1e8/0x370 fs/namei.c:445
 may_create fs/namei.c:2858 [inline]
 vfs_mkdir+0x190/0x390 fs/namei.c:3802
 do_mkdirat+0x1ac/0x1f0 fs/namei.c:3842
 __do_sys_mkdir fs/namei.c:3858 [inline]
 __se_sys_mkdir fs/namei.c:3856 [inline]
 __x64_sys_mkdir+0x40/0x50 fs/namei.c:3856
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8881254973e0 of 4 bytes by task 7995 on cpu 0:
 set_inode_attr fs/kernfs/inode.c:162 [inline]
 kernfs_refresh_inode+0x7a/0x140 fs/kernfs/inode.c:178
 kernfs_iop_permission+0x66/0xa0 fs/kernfs/inode.c:283
 do_inode_permission fs/namei.c:384 [inline]
 inode_permission+0x241/0x370 fs/namei.c:449
 may_lookup fs/namei.c:1696 [inline]
 link_path_walk.part.0+0x622/0xa90 fs/namei.c:2071
 link_path_walk fs/namei.c:2059 [inline]
 path_mountpoint+0x94/0xdb0 fs/namei.c:2701
 filename_mountpoint+0x134/0x270 fs/namei.c:2724
 user_path_mountpoint_at+0x43/0x60 fs/namei.c:2754
 ksys_umount+0xdb/0xab0 fs/namespace.c:1683
 __do_sys_umount fs/namespace.c:1709 [inline]
 __se_sys_umount fs/namespace.c:1707 [inline]
 __x64_sys_umount+0x3a/0x50 fs/namespace.c:1707
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7995 Comm: syz-executor.3 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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