[moderation] [fs?] KCSAN: data-race in d_alloc_parallel / d_set_d_op (12)

[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=1536d7a4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e9dd6c7eeba2114e
dashboard link: https://syzkaller.appspot.com/bug?extid=679899c675d13c2f2721
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [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+679899...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in d_alloc_parallel / d_set_d_op

read-write to 0xffff888106543180 of 4 bytes by task 4406 on cpu 1:
d_set_d_op+0xfb/0x1f0 fs/dcache.c:1831
proc_pident_instantiate+0x164/0x180 fs/proc/base.c:2712
proc_pident_lookup+0x11d/0x190 fs/proc/base.c:2735
proc_tgid_base_lookup+0x2b/0x40 fs/proc/base.c:3458
__lookup_slow+0x18a/0x250 fs/namei.c:1793
lookup_slow+0x3c/0x60 fs/namei.c:1810
walk_component fs/namei.c:2114 [inline]
link_path_walk+0x668/0x830 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

read to 0xffff888106543180 of 4 bytes by task 4405 on cpu 0:
d_in_lookup include/linux/dcache.h:390 [inline]
d_wait_lookup fs/dcache.c:2488 [inline]
d_alloc_parallel+0x5dc/0xc80 fs/dcache.c:2576
__lookup_slow+0x8d/0x250 fs/namei.c:1778
lookup_slow+0x3c/0x60 fs/namei.c:1810
walk_component fs/namei.c:2114 [inline]
link_path_walk+0x668/0x830 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

value changed: 0x10000000 -> 0x1000000c

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 4405 Comm: syz.0.291 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.