syzbot

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BUG: KCSAN: data-race in lookup_fast / shrink_dentry_list

read-write to 0xffff888108061f00 of 4 bytes by task 23990 on cpu 0:
 d_shrink_del fs/dcache.c:449 [inline]
 shrink_dentry_list+0x19f/0x3e0 fs/dcache.c:1074
 shrink_dcache_sb+0x165/0x2a0 fs/dcache.c:1195
 reconfigure_super+0x3fe/0x5a0 fs/super.c:1049
 do_remount fs/namespace.c:2892 [inline]
 path_mount+0x96e/0xb30 fs/namespace.c:3671
 do_mount fs/namespace.c:3692 [inline]
 __do_sys_mount fs/namespace.c:3898 [inline]
 __se_sys_mount+0x27f/0x2d0 fs/namespace.c:3875
 __x64_sys_mount+0x67/0x80 fs/namespace.c:3875
 x64_sys_call+0x2591/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888108061f00 of 4 bytes by task 22979 on cpu 1:
 d_revalidate fs/namei.c:860 [inline]
 lookup_fast+0xd9/0x2a0 fs/namei.c:1641
 walk_component+0x3f/0x230 fs/namei.c:2000
 lookup_last fs/namei.c:2461 [inline]
 path_lookupat+0x10a/0x2b0 fs/namei.c:2485
 filename_lookup+0x127/0x300 fs/namei.c:2514
 vfs_statx+0xa2/0x320 fs/stat.c:244
 vfs_fstatat+0xcd/0x100 fs/stat.c:304
 __do_sys_newfstatat fs/stat.c:468 [inline]
 __se_sys_newfstatat+0x58/0x260 fs/stat.c:462
 __x64_sys_newfstatat+0x55/0x70 fs/stat.c:462
 x64_sys_call+0x25ff/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:263
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00680440 -> 0x00008040

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 22979 Comm: syz-executor.3 Tainted: G        W          6.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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EXT4-fs (loop3): unmounting filesystem 00000000-0000-0000-0000-000000000000.
EXT4-fs (loop3): unmounting filesystem 00000000-0000-0000-0000-000000000000.
EXT4-fs (loop3): unmounting filesystem 00000000-0000-0000-0000-000000000000.