[moderation] [fs?] KCSAN: data-race in __dentry_kill / proc_sys_compare

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4cbfe4502e3d Merge tag 'v7.1-rc5-ksmbd-server-fixes' of gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17de8d36580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d830408e2d151f21
dashboard link: https://syzkaller.appspot.com/bug?extid=6eae17413a5c67bc7a16
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
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/0d167643eef1/disk-4cbfe450.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ef2e6fb19715/vmlinux-4cbfe450.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a44571070b5c/bzImage-4cbfe450.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6eae17...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __dentry_kill / proc_sys_compare

write to 0xffff888107dfed80 of 4 bytes by task 12 on cpu 1:
d_lru_del fs/dcache.c:513 [inline]
__dentry_kill+0xab/0x4d0 fs/dcache.c:713
finish_dput+0x2b/0x200 fs/dcache.c:927
dput+0x52/0x60 fs/dcache.c:976
proc_invalidate_siblings_dcache+0x1d0/0x2b0 fs/proc/inode.c:143
proc_sys_invalidate_dcache fs/proc/proc_sysctl.c:289 [inline]
start_unregistering fs/proc/proc_sysctl.c:316 [inline]
drop_sysctl_table+0xbd/0x270 fs/proc/proc_sysctl.c:1517
drop_sysctl_table+0x1cb/0x270 fs/proc/proc_sysctl.c:1524
drop_sysctl_table+0x1cb/0x270 fs/proc/proc_sysctl.c:1524
drop_sysctl_table+0x1cb/0x270 fs/proc/proc_sysctl.c:1524
unregister_sysctl_table+0x30/0x50 fs/proc/proc_sysctl.c:1542
unregister_net_sysctl_table+0x15/0x20 net/sysctl_net.c:177
__devinet_sysctl_unregister net/ipv4/devinet.c:2735 [inline]
devinet_exit_net+0x10a/0x190 net/ipv4/devinet.c:2897
ops_exit_list net/core/net_namespace.c:199 [inline]
ops_undo_list+0x285/0x420 net/core/net_namespace.c:252
cleanup_net+0x37c/0x5b0 net/core/net_namespace.c:702
process_one_work kernel/workqueue.c:3314 [inline]
process_scheduled_works+0x4f0/0x9c0 kernel/workqueue.c:3397
worker_thread+0x58a/0x780 kernel/workqueue.c:3478
kthread+0x22a/0x280 kernel/kthread.c:436
ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff888107dfed80 of 4 bytes by task 3544 on cpu 0:
d_in_lookup include/linux/dcache.h:403 [inline]
proc_sys_compare+0x85/0x170 fs/proc/proc_sysctl.c:926
__d_lookup_rcu_op_compare+0x207/0x270 fs/dcache.c:2332
__d_lookup_rcu+0x2bf/0x2d0 fs/dcache.c:2384
d_alloc_parallel+0x247/0xce0 fs/dcache.c:2690
__lookup_slow+0x96/0x260 fs/namei.c:1900
lookup_slow+0x3c/0x60 fs/namei.c:1932
walk_component fs/namei.c:2278 [inline]
link_path_walk+0x946/0xe30 fs/namei.c:2652
path_openat+0x1c6/0x2050 fs/namei.c:4854
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: 0x0014000e -> 0x0000400e

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3544 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
==================================================================


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