syzbot

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BUG: KCSAN: data-race in dentry_lru_isolate_shrink / dput

write to 0xffff8880b62d10c0 of 4 bytes by task 23232 on cpu 0:
 d_lru_shrink_move fs/dcache.c:453 [inline]
 dentry_lru_isolate_shrink+0x7b/0x100 fs/dcache.c:1240
 __list_lru_walk_one+0xfb/0x320 mm/list_lru.c:222
 list_lru_walk_one mm/list_lru.c:266 [inline]
 list_lru_walk_node+0x63/0x1a0 mm/list_lru.c:295
 list_lru_walk include/linux/list_lru.h:215 [inline]
 shrink_dcache_sb+0x97/0x1c0 fs/dcache.c:1259
 reconfigure_super+0x267/0x4d0 fs/super.c:940
 do_remount fs/namespace.c:2612 [inline]
 do_mount+0x1384/0x1c00 fs/namespace.c:3191
 __do_sys_mount fs/namespace.c:3410 [inline]
 __se_sys_mount+0xd3/0x100 fs/namespace.c:3387
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3387
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880b62d10c0 of 4 bytes by task 8855 on cpu 1:
 fast_dput fs/dcache.c:746 [inline]
 dput+0x2f/0x420 fs/dcache.c:865
 step_into+0x1ab/0xe70 fs/namei.c:1699
 handle_lookup_down fs/namei.c:2316 [inline]
 path_lookupat+0x4a0/0x560 fs/namei.c:2342
 filename_lookup+0xf2/0x380 fs/namei.c:2366
 user_path_at_empty+0x3b/0x50 fs/namei.c:2646
 user_path_at include/linux/namei.h:59 [inline]
 ksys_umount+0xc2/0xa80 fs/namespace.c:1733
 __do_sys_umount fs/namespace.c:1759 [inline]
 __se_sys_umount fs/namespace.c:1757 [inline]
 __x64_sys_umount+0x2c/0x40 fs/namespace.c:1757
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 8855 Comm: syz-executor.1 Not tainted 5.8.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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