[moderation] [fs?] KCSAN: data-race in d_invalidate / fast_dput

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 54be6c6c5ae8 Linux 6.8-rc3
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=113f853fe80000
kernel config: https://syzkaller.appspot.com/x/.config?x=3cd0dc1b46a5bc5c
dashboard link: https://syzkaller.appspot.com/bug?extid=b90e1920cb0516af822c
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [bra...@kernel.org ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/148fa7492b49/disk-54be6c6c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cfb5e0d97c64/vmlinux-54be6c6c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4eff3a827e09/bzImage-54be6c6c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b90e19...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in d_invalidate / fast_dput

write to 0xffff888153b25c10 of 8 bytes by task 2943 on cpu 0:
__d_drop fs/dcache.c:509 [inline]
d_invalidate+0x59/0x1c0 fs/dcache.c:1585
lookup_fast+0x244/0x290 fs/namei.c:1658
open_last_lookups fs/namei.c:3533 [inline]
path_openat+0x446/0x1d40 fs/namei.c:3795
do_filp_open+0xf6/0x200 fs/namei.c:3825
do_sys_openat2+0xab/0x110 fs/open.c:1404
do_sys_open fs/open.c:1419 [inline]
__do_sys_openat fs/open.c:1435 [inline]
__se_sys_openat fs/open.c:1430 [inline]
__x64_sys_openat+0xf3/0x120 fs/open.c:1430
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+0x63/0x6b

read to 0xffff888153b25c10 of 8 bytes by task 2944 on cpu 1:
hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
d_unhashed include/linux/dcache.h:341 [inline]
retain_dentry fs/dcache.c:686 [inline]
fast_dput+0x62/0x2b0 fs/dcache.c:782
dput+0x24/0xc0 fs/dcache.c:839
path_put fs/namei.c:562 [inline]
terminate_walk+0xf2/0x270 fs/namei.c:686
path_openat+0x1923/0x1d40 fs/namei.c:3799
do_filp_open+0xf6/0x200 fs/namei.c:3825
do_sys_openat2+0xab/0x110 fs/open.c:1404
do_sys_open fs/open.c:1419 [inline]
__do_sys_openat fs/open.c:1435 [inline]
__se_sys_openat fs/open.c:1430 [inline]
__x64_sys_openat+0xf3/0x120 fs/open.c:1430
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+0x63/0x6b

value changed: 0xffff88823767cdc0 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 2944 Comm: syz-executor.0 Not tainted 6.8.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
==================================================================


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