syzbot

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BUG: KCSAN: data-race in dput / shrink_dentry_list

write to 0xffff888134583840 of 4 bytes by task 32684 on cpu 0:
 shrink_dentry_list+0x127/0x540 fs/dcache.c:423
 shrink_dcache_sb+0x188/0x2d0 fs/dcache.c:1296
 reconfigure_super+0x146/0x540 fs/super.c:891
 do_remount fs/namespace.c:2656 [inline]
 path_mount+0x13f9/0x1c40 fs/namespace.c:3316
 do_mount fs/namespace.c:3337 [inline]
 __do_sys_mount fs/namespace.c:3545 [inline]
 __se_sys_mount+0x24b/0x2f0 fs/namespace.c:3522
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3522
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888134583840 of 4 bytes by task 32701 on cpu 1:
 fast_dput fs/dcache.c:749 [inline]
 dput+0x34/0x430 fs/dcache.c:875
 path_put+0x1b/0x30 fs/namei.c:557
 free_fs_struct fs/fs_struct.c:91 [inline]
 exit_fs+0xb3/0xe0 fs/fs_struct.c:108
 do_exit+0x637/0x17a0 kernel/exit.c:828
 do_group_exit+0xce/0x180 kernel/exit.c:929
 get_signal+0xfc3/0x1550 kernel/signal.c:2852
 arch_do_signal_or_restart+0x8c/0x2e0 arch/x86/kernel/signal.c:868
 handle_signal_work kernel/entry/common.c:148 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
 exit_to_user_mode_prepare+0x113/0x190 kernel/entry/common.c:207
 __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:300
 do_syscall_64+0x50/0xd0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00280400 -> 0x00200000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 32701 Comm: syz-executor.5 Tainted: G        W         5.16.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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