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BUG: KCSAN: data-race in kernfs_refresh_inode / tomoyo_realpath_from_path

write to 0xffff888125b08248 of 2 bytes by task 7294 on cpu 0:
 kernfs_refresh_inode+0x42/0x140 fs/kernfs/inode.c:172
 kernfs_iop_permission+0x66/0xa0 fs/kernfs/inode.c:283
 do_inode_permission fs/namei.c:384 [inline]
 inode_permission+0x241/0x3c0 fs/namei.c:449
 may_open.isra.0+0x144/0x250 fs/namei.c:2963
 do_last fs/namei.c:3404 [inline]
 path_openat+0xf07/0x36e0 fs/namei.c:3525
 do_filp_open+0x11e/0x1b0 fs/namei.c:3555
 do_sys_open+0x3b3/0x4f0 fs/open.c:1097
 __do_sys_open fs/open.c:1115 [inline]
 __se_sys_open fs/open.c:1110 [inline]
 __x64_sys_open+0x55/0x70 fs/open.c:1110
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888125b08248 of 2 bytes by task 7151 on cpu 1:
 tomoyo_get_absolute_path security/tomoyo/realpath.c:104 [inline]
 tomoyo_realpath_from_path+0x441/0x4c0 security/tomoyo/realpath.c:304
 tomoyo_mount_acl+0xdd/0x590 security/tomoyo/mount.c:105
 tomoyo_mount_permission+0xef/0x350 security/tomoyo/mount.c:237
 tomoyo_sb_mount+0x3e/0x60 security/tomoyo/tomoyo.c:400
 security_sb_mount+0x81/0xc0 security/security.c:860
 do_mount+0x129/0x15a0 fs/namespace.c:3085
 ksys_mount+0xe8/0x160 fs/namespace.c:3352
 __do_sys_mount fs/namespace.c:3366 [inline]
 __se_sys_mount fs/namespace.c:3363 [inline]
 __x64_sys_mount+0x70/0x90 fs/namespace.c:3363
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7151 Comm: syz-executor.2 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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