[v5.15] KASAN: global-out-of-bounds Read in kernfs_find_ns

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 98f47d0e9b8c Linux 5.15.184
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10a5b482580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6d966a9f787a9782
dashboard link: https://syzkaller.appspot.com/bug?extid=0c0179aeaef8064ef0bc
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5e51314fa9b0/disk-98f47d0e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3348ed80ea4e/vmlinux-98f47d0e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3e02a814f2cc/bzImage-98f47d0e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0c0179...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: global-out-of-bounds in kernfs_name_compare fs/kernfs/dir.c:326 [inline]
BUG: KASAN: global-out-of-bounds in kernfs_find_ns+0x473/0x510 fs/kernfs/dir.c:827
Read of size 4 at addr ffffffff8c4bbf68 by task syz-executor/4169

CPU: 1 PID: 4169 Comm: syz-executor Not tainted 5.15.184-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
print_address_description+0x60/0x2d0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:434 [inline]
kasan_report+0xdf/0x130 mm/kasan/report.c:451
kernfs_name_compare fs/kernfs/dir.c:326 [inline]
kernfs_find_ns+0x473/0x510 fs/kernfs/dir.c:827
kernfs_remove_by_name_ns+0x37/0x100 fs/kernfs/dir.c:1563
kernfs_remove_by_name include/linux/kernfs.h:598 [inline]
remove_files fs/sysfs/group.c:28 [inline]
sysfs_remove_group+0xf8/0x290 fs/sysfs/group.c:289
sysfs_remove_groups+0x50/0xa0 fs/sysfs/group.c:313
device_del+0x620/0xa70 drivers/base/core.c:3599
unregister_netdevice_many+0x141e/0x18f0 net/core/dev.c:11161
unregister_netdevice_queue+0x31c/0x360 net/core/dev.c:11067
unregister_netdevice include/linux/netdevice.h:3020 [inline]
__tun_detach+0xd4a/0x1500 drivers/net/tun.c:686
tun_detach drivers/net/tun.c:702 [inline]
tun_chr_close+0x109/0x1b0 drivers/net/tun.c:3440
__fput+0x234/0x930 fs/file_table.c:311
task_work_run+0x125/0x1a0 kernel/task_work.c:188
exit_task_work include/linux/task_work.h:33 [inline]
do_exit+0x616/0x20a0 kernel/exit.c:874
do_group_exit+0x12e/0x300 kernel/exit.c:996
__do_sys_exit_group kernel/exit.c:1007 [inline]
__se_sys_exit_group kernel/exit.c:1005 [inline]
__x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1005
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fbefd3b0969
Code: Unable to access opcode bytes at RIP 0x7fbefd3b093f.
RSP: 002b:00007ffef7c1c068 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007fbefd432921 RCX: 00007fbefd3b0969
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: 0000000000000027 R08: 00007ffef7c19e06 R09: 00007ffef7c1d320
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffef7c1d320
R13: 00007fbefd43289d R14: 0000555590ec54a8 R15: 00007ffef7c1f4e0
</TASK>

The buggy address belongs to the variable:
jfs_fs_type+0xe8/0x2a0

Memory state around the buggy address:
ffffffff8c4bbe00: 00 00 00 00 00 00 00 00 04 f9 f9 f9 00 00 00 00
ffffffff8c4bbe80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffffff8c4bbf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 f9 f9 f9
^
ffffffff8c4bbf80: f9 f9 f9 f9 00 00 00 00 00 00 00 00 00 00 00 00
ffffffff8c4bc000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.