[syzbot] [cgroups?] WARNING in cgroup_file_release

[syzbot <syzbot+da9171e60819297fc1d3@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    9c0826a5d9aa Add linux-next specific files for 20251107
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12a5d0b4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4f8fcc6438a785e7
dashboard link: https://syzkaller.appspot.com/bug?extid=da9171e60819297fc1d3
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6b76dc0ec17f/disk-9c0826a5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/522b6d2a1d1d/vmlinux-9c0826a5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4a58225d70f3/bzImage-9c0826a5.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+da9171e60819297fc1d3@syzkaller.appspotmail.com

netlink: 16 bytes leftover after parsing attributes in process `syz.2.623'.
------------[ cut here ]------------
WARNING: ./include/linux/ns_common.h:255 at __ns_ref_put include/linux/ns_common.h:255 [inline], CPU#1: syz.2.623/8079
WARNING: ./include/linux/ns_common.h:255 at put_cgroup_ns include/linux/cgroup_namespace.h:39 [inline], CPU#1: syz.2.623/8079
WARNING: ./include/linux/ns_common.h:255 at cgroup_file_release+0x196/0x1d0 kernel/cgroup/cgroup.c:4282, CPU#1: syz.2.623/8079
Modules linked in:
CPU: 1 UID: 0 PID: 8079 Comm: syz.2.623 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:__ns_ref_put include/linux/ns_common.h:255 [inline]
RIP: 0010:put_cgroup_ns include/linux/cgroup_namespace.h:39 [inline]
RIP: 0010:cgroup_file_release+0x196/0x1d0 kernel/cgroup/cgroup.c:4282
Code: 3b 00 74 08 4c 89 ef e8 a8 44 6e 00 49 c7 45 00 00 00 00 00 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc e8 bb d8 07 00 90 <0f> 0b 90 eb 9d e8 b0 d8 07 00 4c 89 e7 be 03 00 00 00 e8 e3 d2 df
RSP: 0018:ffffc9000eaef8c8 EFLAGS: 00010293
RAX: ffffffff81b9f775 RBX: 1ffff1100bc32a83 RCX: ffff88802990db80
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 0000000000000000
RBP: 00000000ffffffff R08: ffff8880796780bb R09: 1ffff1100f2cf017
R10: dffffc0000000000 R11: ffffed100f2cf018 R12: ffff8880796780b8
R13: ffff88805e195418 R14: ffff88805c63a100 R15: ffff888079678000
FS:  0000000000000000(0000) GS:ffff888125b79000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000000011c0 CR3: 000000007b8ee000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 kernfs_release_file+0x131/0x2d0 fs/kernfs/file.c:764
 kernfs_fop_release+0x113/0x190 fs/kernfs/file.c:779
 __fput+0x44c/0xa70 fs/file_table.c:468
 task_work_run+0x1d4/0x260 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x6bd/0x2300 kernel/exit.c:970
 do_group_exit+0x21c/0x2d0 kernel/exit.c:1111
 get_signal+0x1285/0x1340 kernel/signal.c:3034
 arch_do_signal_or_restart+0x9a/0x7a0 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
 exit_to_user_mode_loop+0x87/0x4f0 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+0x2e9/0xfa0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9b5b38f6c9
Code: Unable to access opcode bytes at 0x7f9b5b38f69f.
RSP: 002b:00007f9b5c2910e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f9b5b5e5fa8 RCX: 00007f9b5b38f6c9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f9b5b5e5fa8
RBP: 00007f9b5b5e5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9b5b5e6038 R14: 00007ffe297b11d0 R15: 00007ffe297b12b8
 </TASK>


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