[moderation] [fs?] KCSAN: data-race in fifo_open / wait_for_partner (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 155a3c003e55 Merge tag 'for-6.16/dm-fixes-2' of git://git...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15b7698c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c8b73fe883c5b6ae
dashboard link: https://syzkaller.appspot.com/bug?extid=4cec0207aa959dfb97a4
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
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/b702b3a60562/disk-155a3c00.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/74f911fca904/vmlinux-155a3c00.xz
kernel image: https://storage.googleapis.com/syzbot-assets/36a9a45ae614/bzImage-155a3c00.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4cec02...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in fifo_open / wait_for_partner

read-write to 0xffff888136be936c of 4 bytes by task 26458 on cpu 0:
fifo_open+0x86/0x5d0 fs/pipe.c:1128
do_dentry_open+0x649/0xa20 fs/open.c:964
vfs_open+0x37/0x1e0 fs/open.c:1094
do_open fs/namei.c:3896 [inline]
path_openat+0x1c5e/0x2170 fs/namei.c:4055
do_filp_open+0x109/0x230 fs/namei.c:4082
do_sys_openat2+0xa6/0x110 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_open fs/open.c:1460 [inline]
__se_sys_open fs/open.c:1456 [inline]
__x64_sys_open+0xe6/0x110 fs/open.c:1456
x64_sys_call+0x14d4/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:3
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888136be936c of 4 bytes by task 26455 on cpu 1:
pipe_unlock fs/pipe.c:97 [inline]
wait_for_partner+0xb5/0x1c0 fs/pipe.c:1102
fifo_open+0x462/0x5d0 fs/pipe.c:1172
do_dentry_open+0x649/0xa20 fs/open.c:964
vfs_open+0x37/0x1e0 fs/open.c:1094
do_open fs/namei.c:3896 [inline]
path_openat+0x1c5e/0x2170 fs/namei.c:4055
do_filp_open+0x109/0x230 fs/namei.c:4082
do_sys_openat2+0xa6/0x110 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0xf2/0x120 fs/open.c:1463
x64_sys_call+0x1af/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:258
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000001 -> 0x00000002

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 26455 Comm: syz.8.6682 Not tainted 6.16.0-rc6-syzkaller-00002-g155a3c003e55 #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================


---
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.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup