[moderation] [ext4?] KCSAN: data-race in __d_instantiate / lookup_fast (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c2d5304e6c64 Merge tag 'platform-drivers-x86-v6.7-2' of gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16edbdd4e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=8c1151391aefc0c3
dashboard link: https://syzkaller.appspot.com/bug?extid=beac8d4434a19593001a
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [adilger...@dilger.ca linux...@vger.kernel.org linux-...@vger.kernel.org linux-...@vger.kernel.org ty...@mit.edu]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/40c3b752a9c1/disk-c2d5304e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6ab3363b9f46/vmlinux-c2d5304e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e1685e2593f6/bzImage-c2d5304e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+beac8d...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __d_instantiate / lookup_fast

read-write to 0xffff888142a35cc0 of 4 bytes by task 7868 on cpu 0:
__d_instantiate+0x2cd/0x3b0 fs/dcache.c:2010
d_instantiate_new+0x5c/0xf0 fs/dcache.c:2054
ext4_mkdir+0x5e5/0x740 fs/ext4/namei.c:3050
vfs_mkdir+0x1ef/0x2f0 fs/namei.c:4106
do_mkdirat+0x12f/0x2a0 fs/namei.c:4129
__do_sys_mkdir fs/namei.c:4149 [inline]
__se_sys_mkdir fs/namei.c:4147 [inline]
__x64_sys_mkdir+0x44/0x50 fs/namei.c:4147
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff888142a35cc0 of 4 bytes by task 7869 on cpu 1:
d_revalidate fs/namei.c:861 [inline]
lookup_fast+0xd9/0x290 fs/namei.c:1643
walk_component+0x3f/0x230 fs/namei.c:1998
lookup_last fs/namei.c:2459 [inline]
path_lookupat+0x10a/0x2a0 fs/namei.c:2483
filename_lookup+0x126/0x300 fs/namei.c:2512
user_path_at_empty+0x42/0x110 fs/namei.c:2911
user_path_at include/linux/namei.h:57 [inline]
do_mount fs/namespace.c:3674 [inline]
__do_sys_mount fs/namespace.c:3886 [inline]
__se_sys_mount+0x24b/0x2d0 fs/namespace.c:3863
__x64_sys_mount+0x67/0x80 fs/namespace.c:3863
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x00000000 -> 0x00280000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7869 Comm: syz-executor.5 Tainted: G W 6.7.0-rc2-syzkaller-00014-gc2d5304e6c64 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
==================================================================


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