[moderation] [fs?] KCSAN: data-race in __d_instantiate / path_openat (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d60bc1401583 Merge tag 'pwrseq-updates-for-v7.1-rc1' of gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17b5feba580000
kernel config: https://syzkaller.appspot.com/x/.config?x=26d067a0cd8bb9d8
dashboard link: https://syzkaller.appspot.com/bug?extid=06faec728cc81c59b6e9
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
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/fc76b34d00fe/disk-d60bc140.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ec1504ae6f57/vmlinux-d60bc140.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6b276cb7cbd9/bzImage-d60bc140.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+06faec...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __d_instantiate / path_openat

write to 0xffff88811b1ee0f0 of 8 bytes by task 15489 on cpu 1:
__d_set_inode_and_type fs/dcache.c:407 [inline]
__d_instantiate+0x1db/0x390 fs/dcache.c:1985
d_make_persistent+0x78/0x110 fs/dcache.c:2803
shmem_mknod+0x15f/0x170 mm/shmem.c:3907
shmem_create+0x34/0x50 mm/shmem.c:3959
lookup_open fs/namei.c:4511 [inline]
open_last_lookups fs/namei.c:4611 [inline]
path_openat+0xd75/0x2050 fs/namei.c:4855
do_file_open+0x16c/0x290 fs/namei.c:4887
do_sys_openat2+0x94/0x130 fs/open.c:1364
do_sys_open fs/open.c:1370 [inline]
__do_sys_openat fs/open.c:1386 [inline]
__se_sys_openat fs/open.c:1381 [inline]
__x64_sys_openat+0xf2/0x120 fs/open.c:1381
x64_sys_call+0x1e39/0x3020 arch/x86/include/generated/asm/syscalls_64.h:258
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811b1ee0f0 of 8 bytes by task 15492 on cpu 0:
lookup_fast_for_open fs/namei.c:4554 [inline]
open_last_lookups fs/namei.c:4582 [inline]
path_openat+0x464/0x2050 fs/namei.c:4855
do_file_open+0x16c/0x290 fs/namei.c:4887
do_sys_openat2+0x94/0x130 fs/open.c:1364
do_sys_open fs/open.c:1370 [inline]
__do_sys_openat fs/open.c:1386 [inline]
__se_sys_openat fs/open.c:1381 [inline]
__x64_sys_openat+0xf2/0x120 fs/open.c:1381
x64_sys_call+0x1e39/0x3020 arch/x86/include/generated/asm/syscalls_64.h:258
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0xffff88812f5eefc0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 15492 Comm: syz.6.2819 Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
==================================================================


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