[moderation] [fs?] KCSAN: data-race in __d_lookup_rcu / __dentry_kill

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6485cf5ea253 Merge tag 'hid-for-linus-2024101301' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1246385f980000
kernel config: https://syzkaller.appspot.com/x/.config?x=fd83253b74c9c570
dashboard link: https://syzkaller.appspot.com/bug?extid=3c1097664a705fd81b39
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/3334c1a19c39/disk-6485cf5e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f61d7fbea9cd/vmlinux-6485cf5e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1165b697b4d7/bzImage-6485cf5e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3c1097...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __d_lookup_rcu / __dentry_kill

read to 0xffff888113d9e3d0 of 8 bytes by task 6465 on cpu 1:
hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
d_unhashed include/linux/dcache.h:354 [inline]
__d_lookup_rcu+0x105/0x2a0 fs/dcache.c:2240
lookup_fast+0x8e/0x2a0 fs/namei.c:1667
lookup_fast_for_open fs/namei.c:3632 [inline]
open_last_lookups fs/namei.c:3665 [inline]
path_openat+0x41e/0x1fa0 fs/namei.c:3930
do_filp_open+0xf7/0x200 fs/namei.c:3960
io_openat2+0x280/0x3a0 io_uring/openclose.c:140
io_issue_sqe+0x181/0xcc0 io_uring/io_uring.c:1739
io_queue_sqe io_uring/io_uring.c:1953 [inline]
io_submit_sqe io_uring/io_uring.c:2209 [inline]
io_submit_sqes+0x6c3/0x1090 io_uring/io_uring.c:2324
__do_sys_io_uring_enter io_uring/io_uring.c:3343 [inline]
__se_sys_io_uring_enter+0x1ce/0x17b0 io_uring/io_uring.c:3279
__x64_sys_io_uring_enter+0x78/0x90 io_uring/io_uring.c:3279
x64_sys_call+0x2567/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:427
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff888113d9e3d0 of 8 bytes by task 6466 on cpu 0:
__d_drop fs/dcache.c:521 [inline]
__dentry_kill+0x13e/0x4c0 fs/dcache.c:613
dput+0x5c/0xd0 fs/dcache.c:857
handle_mounts fs/namei.c:1579 [inline]
step_into+0x21a/0x810 fs/namei.c:1891
open_last_lookups fs/namei.c:3721 [inline]
path_openat+0x1234/0x1fa0 fs/namei.c:3930
do_filp_open+0xf7/0x200 fs/namei.c:3960
io_openat2+0x280/0x3a0 io_uring/openclose.c:140
io_issue_sqe+0x181/0xcc0 io_uring/io_uring.c:1739
io_wq_submit_work+0x474/0x5f0 io_uring/io_uring.c:1848
io_worker_handle_work+0x486/0x9d0 io_uring/io-wq.c:601
io_wq_worker+0x286/0x820 io_uring/io-wq.c:655
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 6466 Comm: iou-wrk-6465 Not tainted 6.12.0-rc3-syzkaller-00007-g6485cf5ea253 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.