syzbot

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BUG: KCSAN: data-race in shrink_dentry_list / step_into

write to 0xffff8881049c2600 of 4 bytes by task 5170 on cpu 0:
 shrink_dentry_list+0x127/0x340 fs/dcache.c:423
 shrink_dcache_sb+0x188/0x2d0 fs/dcache.c:1296
 reconfigure_super+0x2aa/0x4f0 fs/super.c:889
 do_remount fs/namespace.c:2650 [inline]
 path_mount+0x145a/0x1d20 fs/namespace.c:3310
 do_mount fs/namespace.c:3331 [inline]
 __do_sys_mount fs/namespace.c:3539 [inline]
 __se_sys_mount+0x24b/0x2f0 fs/namespace.c:3516
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3516
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881049c2600 of 4 bytes by task 22442 on cpu 1:
 __follow_mount_rcu fs/namei.c:1429 [inline]
 handle_mounts fs/namei.c:1486 [inline]
 step_into+0x103/0xee0 fs/namei.c:1800
 walk_component+0x1a1/0x360 fs/namei.c:1976
 link_path_walk+0x4ae/0x770
 path_lookupat+0x8b/0x3d0 fs/namei.c:2448
 filename_lookup+0x130/0x310 fs/namei.c:2478
 user_path_at_empty+0x3e/0x110 fs/namei.c:2801
 user_path_at include/linux/namei.h:57 [inline]
 vfs_statx+0xa9/0x2a0 fs/stat.c:221
 vfs_fstatat fs/stat.c:243 [inline]
 vfs_lstat include/linux/fs.h:3356 [inline]
 __do_sys_newlstat fs/stat.c:398 [inline]
 __se_sys_newlstat+0x5d/0x250 fs/stat.c:392
 __x64_sys_newlstat+0x2d/0x40 fs/stat.c:392
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00280400 -> 0x00200000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 22442 Comm: syz-executor.3 Not tainted 5.15.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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