[moderation] [fs?] KCSAN: data-race in __d_lookup_rcu / __d_rehash (8)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d082ecbc71e9 Linux 6.14-rc4
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14a9adb0580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e9dd6c7eeba2114e
dashboard link: https://syzkaller.appspot.com/bug?extid=7bc7bce232272a1d0290
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [h...@lst.de jl...@evilplan.org linux-...@vger.kernel.org linux-...@vger.kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2b352c2abb77/disk-d082ecbc.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c5f4a062a264/vmlinux-d082ecbc.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c3a86625df5a/bzImage-d082ecbc.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7bc7bc...@syzkaller.appspotmail.com

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

read to 0xffff88810625f190 of 8 bytes by task 6549 on cpu 1:
hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
d_unhashed include/linux/dcache.h:366 [inline]
__d_lookup_rcu+0x105/0x2a0 fs/dcache.c:2267
lookup_fast+0x99/0x320 fs/namei.c:1727
walk_component fs/namei.c:2110 [inline]
link_path_walk+0x472/0x830 fs/namei.c:2479
path_openat+0x1af/0x1fc0 fs/namei.c:3985
do_filp_open+0x107/0x230 fs/namei.c:4016
do_sys_openat2+0xab/0x120 fs/open.c:1428
do_sys_open fs/open.c:1443 [inline]
__do_sys_openat fs/open.c:1459 [inline]
__se_sys_openat fs/open.c:1454 [inline]
__x64_sys_openat+0xf3/0x120 fs/open.c:1454
x64_sys_call+0x2b30/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:258
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 0xffff88810625f190 of 8 bytes by task 6617 on cpu 0:
hlist_bl_add_head_rcu include/linux/rculist_bl.h:81 [inline]
__d_rehash+0xa9/0x210 fs/dcache.c:2448
__d_add+0x373/0x4a0 fs/dcache.c:2663
d_add+0x45/0x50 fs/dcache.c:2686
configfs_lookup+0x1ab/0x440 fs/configfs/dir.c:499
lookup_one_qstr_excl+0xca/0x1c0 fs/namei.c:1693
do_unlinkat+0x144/0x4d0 fs/namei.c:4577
__do_sys_unlink fs/namei.c:4637 [inline]
__se_sys_unlink fs/namei.c:4635 [inline]
__x64_sys_unlink+0x2e/0x40 fs/namei.c:4635
x64_sys_call+0x2329/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:88
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

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 6617 Comm: syz-executor Not tainted 6.14.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
==================================================================


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[syzbot]

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