[moderation] [fs?] KCSAN: data-race in __d_drop / __d_lookup (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 18f7fcd5e69a Linux 6.19-rc8
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12b2dc52580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8e27f4588a0f2183
dashboard link: https://syzkaller.appspot.com/bug?extid=3df9f544e43fcbd315d7
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/8157f3acb6cd/disk-18f7fcd5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0ac01f41d27b/vmlinux-18f7fcd5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f87453c1c5ae/bzImage-18f7fcd5.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3df9f5...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __d_drop / __d_lookup

write to 0xffff8881076ccb50 of 8 bytes by task 31 on cpu 1:
__hlist_bl_del include/linux/list_bl.h:128 [inline]
___d_drop fs/dcache.c:568 [inline]
__d_drop+0xf7/0x240 fs/dcache.c:575
d_invalidate+0x50/0x1d0 fs/dcache.c:1701
proc_invalidate_siblings_dcache+0x1c8/0x2b0 fs/proc/inode.c:142
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:2700 [inline]
devinet_exit_net+0x10a/0x190 net/ipv4/devinet.c:2863
ops_exit_list net/core/net_namespace.c:199 [inline]
ops_undo_list+0x285/0x420 net/core/net_namespace.c:252
cleanup_net+0x31c/0x550 net/core/net_namespace.c:696
process_one_work kernel/workqueue.c:3257 [inline]
process_scheduled_works+0x4cd/0x9d0 kernel/workqueue.c:3340
worker_thread+0x6bc/0x8b0 kernel/workqueue.c:3421
kthread+0x488/0x510 kernel/kthread.c:463
ret_from_fork+0x148/0x280 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

read to 0xffff8881076ccb50 of 8 bytes by task 3039 on cpu 0:
hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
d_unhashed include/linux/dcache.h:366 [inline]
__d_lookup+0xf8/0x340 fs/dcache.c:2455
lookup_fast+0x5e/0x320 fs/namei.c:1824
walk_component fs/namei.c:2225 [inline]
link_path_walk+0x51c/0xe30 fs/namei.c:2597
path_openat+0x1bf/0x23c0 fs/namei.c:4792
do_filp_open+0x15d/0x280 fs/namei.c:4823
do_sys_openat2+0xa6/0x150 fs/open.c:1430
do_sys_open fs/open.c:1436 [inline]
__do_sys_openat fs/open.c:1452 [inline]
__se_sys_openat fs/open.c:1447 [inline]
__x64_sys_openat+0xf2/0x120 fs/open.c:1447
x64_sys_call+0x2b07/0x3000 arch/x86/include/generated/asm/syscalls_64.h:258
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff88811a898d88 -> 0xffff88811a96da88

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3039 Comm: dhcpcd Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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