KCSAN: data-race in __d_lookup_rcu / __d_rehash (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dc164f4fb00a Merge tag 'for-linus-6.0-rc7' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1346ce64880000
kernel config: https://syzkaller.appspot.com/x/.config?x=8afb86a3b3410984
dashboard link: https://syzkaller.appspot.com/bug?extid=f8ea0aa0e0fbd5005320
compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
CC: [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/a9149ed151ce/disk-dc164f4f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c34fad522ff9/vmlinux-dc164f4f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f8ea0a...@syzkaller.appspotmail.com

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

read to 0xffff8881060d0b50 of 8 bytes by task 8270 on cpu 0:
hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
d_unhashed include/linux/dcache.h:334 [inline]
__d_lookup_rcu+0x12e/0x2a0 fs/dcache.c:2400
lookup_fast+0x8a/0x270 fs/namei.c:1620
walk_component fs/namei.c:1989 [inline]
link_path_walk+0x439/0x8a0 fs/namei.c:2320
path_openat+0x19c/0x1b00 fs/namei.c:3687
do_filp_open+0x105/0x220 fs/namei.c:3718
do_sys_openat2+0xb5/0x2a0 fs/open.c:1313
do_sys_open fs/open.c:1329 [inline]
__do_sys_openat fs/open.c:1345 [inline]
__se_sys_openat fs/open.c:1340 [inline]
__x64_sys_openat+0xef/0x110 fs/open.c:1340
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

write to 0xffff8881060d0b50 of 8 bytes by task 8610 on cpu 1:
hlist_bl_add_head_rcu include/linux/rculist_bl.h:81 [inline]
__d_rehash+0xb9/0x1f0 fs/dcache.c:2579
__d_add+0x36d/0x4a0 fs/dcache.c:2803
d_add+0x41/0x50 fs/dcache.c:2826
simple_lookup+0x85/0x90 fs/libfs.c:75
__lookup_hash+0xbc/0x180 fs/namei.c:1601
do_unlinkat+0x14b/0x510 fs/namei.c:4281
__do_sys_unlink fs/namei.c:4345 [inline]
__se_sys_unlink fs/namei.c:4343 [inline]
__x64_sys_unlink+0x2c/0x30 fs/namei.c:4343
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 8610 Comm: udevd Not tainted 6.0.0-rc6-syzkaller-00045-gdc164f4fb00a-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2022
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

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