[moderation] [fs?] KCSAN: data-race in d_invalidate / fast_dput (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0048fbb4011e Merge tag 'locking-futex-2025-12-10' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1552c61a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=9230b46da882b43c
dashboard link: https://syzkaller.appspot.com/bug?extid=70bb80293ee8e5c119bf
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
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/e633d71eed8d/disk-0048fbb4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/828a01d70d23/vmlinux-0048fbb4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/658743f84096/bzImage-0048fbb4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+70bb80...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in d_invalidate / fast_dput

write to 0xffff888105f89490 of 8 bytes by task 4879 on cpu 1:
__d_drop fs/dcache.c:576 [inline]
d_invalidate+0x5b/0x200 fs/dcache.c:1691
proc_invalidate_siblings_dcache+0x1c0/0x2a0 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
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_sysctl_unregister net/ipv4/devinet.c:2728 [inline]
inetdev_destroy net/ipv4/devinet.c:334 [inline]
inetdev_event+0x6e4/0xba0 net/ipv4/devinet.c:1655
notifier_call_chain kernel/notifier.c:85 [inline]
raw_notifier_call_chain+0x6f/0x1b0 kernel/notifier.c:453
call_netdevice_notifiers_info net/core/dev.c:2230 [inline]
call_netdevice_notifiers_extack net/core/dev.c:2268 [inline]
call_netdevice_notifiers net/core/dev.c:2282 [inline]
unregister_netdevice_many_notify+0xea0/0x16d0 net/core/dev.c:12381
unregister_netdevice_many net/core/dev.c:12444 [inline]
unregister_netdevice_queue net/core/dev.c:12258 [inline]
unregister_netdevice include/linux/netdevice.h:3405 [inline]
unregister_netdev+0x14c/0x1b0 net/core/dev.c:12462
slip_close+0xe4/0x100 drivers/net/slip/slip.c:906
tty_ldisc_close drivers/tty/tty_ldisc.c:455 [inline]
tty_ldisc_kill+0x8d/0x140 drivers/tty/tty_ldisc.c:613
tty_ldisc_release+0x171/0x1d0 drivers/tty/tty_ldisc.c:781
tty_release_struct+0x1d/0xb0 drivers/tty/tty_io.c:1681
tty_release+0x856/0xb10 drivers/tty/tty_io.c:1852
__fput+0x29b/0x650 fs/file_table.c:468
____fput+0x1c/0x30 fs/file_table.c:496
task_work_run+0x131/0x1a0 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:44 [inline]
exit_to_user_mode_loop+0x1fe/0x740 kernel/entry/common.c:75
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
do_syscall_64+0x202/0x2a0 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888105f89490 of 8 bytes by task 3045 on cpu 0:
hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
d_unhashed include/linux/dcache.h:366 [inline]
retain_dentry fs/dcache.c:753 [inline]
fast_dput+0x5f/0x2c0 fs/dcache.c:849
dput+0x24/0x60 fs/dcache.c:924
path_put fs/namei.c:665 [inline]
terminate_walk+0x77/0x210 fs/namei.c:792
path_openat+0x1e40/0x23b0 fs/namei.c:4788
do_filp_open+0x109/0x230 fs/namei.c:4814
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+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff888237a4f478 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3045 Comm: dhcpcd Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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