[syzbot] [fs?] WARNING in nsproxy_ns_active_get

[syzbot <syzbot+0a8655a80e189278487e@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    17490bd0527f Add linux-next specific files for 20251104
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1006532f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9995c0d2611ab121
dashboard link: https://syzkaller.appspot.com/bug?extid=0a8655a80e189278487e
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1406532f980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1166ff34580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a4d318147846/disk-17490bd0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/86641a470170/vmlinux-17490bd0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/35c008a540c8/bzImage-17490bd0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0a8655a80e189278487e@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: ./include/linux/ns_common.h:288 at __ns_ref_active_get include/linux/ns_common.h:288 [inline], CPU#1: syz.0.20/6007
WARNING: ./include/linux/ns_common.h:288 at nsproxy_ns_active_get+0x8ab/0xcb0 fs/nsfs.c:690, CPU#1: syz.0.20/6007
Modules linked in:
CPU: 1 UID: 0 PID: 6007 Comm: syz.0.20 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:__ns_ref_active_get include/linux/ns_common.h:288 [inline]
RIP: 0010:nsproxy_ns_active_get+0x8ab/0xcb0 fs/nsfs.c:690
Code: 5f 5d e9 08 ca 18 09 cc e8 32 8c 77 ff 90 0f 0b 90 e9 ee f7 ff ff e8 24 8c 77 ff 90 0f 0b 90 e9 12 f8 ff ff e8 16 8c 77 ff 90 <0f> 0b 90 e9 dc f8 ff ff e8 08 8c 77 ff 90 0f 0b 90 e9 03 f9 ff ff
RSP: 0018:ffffc900039cfd40 EFLAGS: 00010293
RAX: ffffffff8249d07a RBX: ffff8880582bb680 RCX: ffff88806aeb5b80
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: 00000000f0000301 R08: ffff88807ca21913 R09: 1ffff1100f944322
R10: dffffc0000000000 R11: ffffed100f944323 R12: dffffc0000000000
R13: 1ffff1100d52d683 R14: ffff88807ca21910 R15: ffff88807ca216c0
FS:  0000555570bd2500(0000) GS:ffff888125b92000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30163fff CR3: 000000007d256000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 switch_task_namespaces+0x3e/0x110 kernel/nsproxy.c:240
 commit_nsset kernel/nsproxy.c:555 [inline]
 __do_sys_setns kernel/nsproxy.c:591 [inline]
 __se_sys_setns+0x784/0x17d0 kernel/nsproxy.c:559
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc583f8f6c9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd2014d848 EFLAGS: 00000246 ORIG_RAX: 0000000000000134
RAX: ffffffffffffffda RBX: 00007fc5841e5fa0 RCX: 00007fc583f8f6c9
RDX: 0000000000000000 RSI: 0000000024020000 RDI: 0000000000000003
RBP: 00007fc584011f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc5841e5fa0 R14: 00007fc5841e5fa0 R15: 0000000000000002
 </TASK>


---
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 syzkaller@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 syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

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