Re: [syzbot] [fs?] WARNING in nsproxy_ns_active_put

[syzbot <syzbot+0b2e79f91ff6579bfa5b@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in alloc_pid

------------[ cut here ]------------
WARNING: ./include/linux/ns_common.h:288 at __ns_ref_active_get include/linux/ns_common.h:288 [inline], CPU#1: syz-executor/6396
WARNING: ./include/linux/ns_common.h:288 at alloc_pid+0xad6/0xc70 kernel/pid.c:285, CPU#1: syz-executor/6396
Modules linked in:
CPU: 1 UID: 0 PID: 6396 Comm: syz-executor 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:alloc_pid+0xad6/0xc70 kernel/pid.c:285
Code: cc e8 7e d6 34 00 be 02 00 00 00 eb 0a e8 72 d6 34 00 be 01 00 00 00 48 89 df e8 05 d8 0c 03 e9 84 fa ff ff e8 5b d6 34 00 90 <0f> 0b 90 e9 2c fd ff ff e8 4d d6 34 00 90 0f 0b 90 e9 5b fd ff ff
RSP: 0018:ffffc900035d79d8 EFLAGS: 00010293
RAX: ffffffff818cf9d5 RBX: ffff888075669998 RCX: ffff8880279b1e80
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: ffff888075cab901 R08: ffff88807566999b R09: 1ffff1100eacd333
R10: dffffc0000000000 R11: ffffed100eacd334 R12: dffffc0000000000
R13: 1ffff1100eb95751 R14: ffff888075669830 R15: dffffc0000000000
FS:  000055556cc43500(0000) GS:ffff888125b79000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7cfd1156c0 CR3: 00000000246e4000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 copy_process+0x18e7/0x3930 kernel/fork.c:2196
 kernel_clone+0x21e/0x840 kernel/fork.c:2609
 __do_sys_clone kernel/fork.c:2750 [inline]
 __se_sys_clone kernel/fork.c:2734 [inline]
 __x64_sys_clone+0x18b/0x1e0 kernel/fork.c:2734
 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: 0033:0x7f7cfc385e13
Code: 1f 84 00 00 00 00 00 64 48 8b 04 25 10 00 00 00 45 31 c0 31 d2 31 f6 bf 11 00 20 01 4c 8d 90 d0 02 00 00 b8 38 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 89 c2 85 c0 75 2c 64 48 8b 04 25 10 00 00
RSP: 002b:00007ffeab10e9d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f7cfc385e13
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000001
R10: 000055556cc437d0 R11: 0000000000000246 R12: 0000000000000000
R13: 00000000000927c0 R14: 0000000000021378 R15: 00007ffeab10eb70
 </TASK>


Tested on:

commit:         9c0826a5 Add linux-next specific files for 20251107
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=162110b4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4f8fcc6438a785e7
dashboard link: https://syzkaller.appspot.com/bug?extid=0b2e79f91ff6579bfa5b
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=12afd812580000