KCSAN: data-race in __mnt_want_write / propagate

Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in __mnt_want_write / propagate_one fs				1	1770d	1770d	0/28	closed as invalid on 2020/06/18 14:13

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BUG: KCSAN: data-race in __mnt_want_write / propagate_one

write to 0xffff8880ab6f8cf0 of 4 bytes by task 13314 on cpu 0:
 propagate_one+0x32d/0x400 fs/pnode.c:267
 propagate_mnt+0x2f8/0x640 fs/pnode.c:319
 attach_recursive_mnt+0x519/0x1210 fs/namespace.c:2129
 graft_tree fs/namespace.c:2237 [inline]
 do_add_mount fs/namespace.c:2783 [inline]
 do_new_mount_fc fs/namespace.c:2822 [inline]
 do_new_mount fs/namespace.c:2876 [inline]
 do_mount+0x1aa8/0x1bd0 fs/namespace.c:3199
 __do_sys_mount fs/namespace.c:3409 [inline]
 __se_sys_mount+0xd3/0x100 fs/namespace.c:3386
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3386
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880ab6f8cf0 of 4 bytes by task 9284 on cpu 1:
 __mnt_is_readonly fs/namespace.c:248 [inline]
 mnt_is_readonly fs/namespace.c:292 [inline]
 __mnt_want_write+0xcc/0x180 fs/namespace.c:332
 touch_atime+0x8c/0x1a0 fs/inode.c:1834
 file_accessed include/linux/fs.h:2229 [inline]
 iterate_dir+0x2c4/0x320 fs/readdir.c:70
 __do_sys_getdents fs/readdir.c:283 [inline]
 __se_sys_getdents+0x7f/0x190 fs/readdir.c:268
 __x64_sys_getdents+0x3f/0x50 fs/readdir.c:268
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 9284 Comm: syz-executor.5 Not tainted 5.8.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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