linux-kernel - [syzbot] [kernel?] WARNING in put_pid

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Message-ID: <691069c5.a70a0220.22f260.00ab.GAE@google.com>
Date: Sun, 09 Nov 2025 02:15:33 -0800
From: syzbot <syzbot+513ead8ebc465c343285@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, luto@...nel.org, peterz@...radead.org, 
	syzkaller-bugs@...glegroups.com, tglx@...utronix.de
Subject: [syzbot] [kernel?] WARNING in put_pid_ns

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=112b2a92580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4f8fcc6438a785e7
dashboard link: https://syzkaller.appspot.com/bug?extid=513ead8ebc465c343285
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+513ead8ebc465c343285@...kaller.appspotmail.com

------------[ cut here ]------------
WARNING: ./include/linux/ns_common.h:255 at __ns_ref_put include/linux/ns_common.h:255 [inline], CPU#1: syz.3.216/6577
WARNING: ./include/linux/ns_common.h:255 at put_pid_ns+0x113/0x150 kernel/pid_namespace.c:187, CPU#1: syz.3.216/6577
Modules linked in:
CPU: 1 UID: 60929 PID: 6577 Comm: syz.3.216 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_pid_ns+0x113/0x150 kernel/pid_namespace.c:187
Code: ab cc ff bf 01 00 00 00 89 ee e8 58 b9 03 00 85 ed 7e 1c e8 0f b5 03 00 5b 41 5e 41 5f 5d c3 cc cc cc cc cc e8 fe b4 03 00 90 <0f> 0b 90 eb 95 e8 f3 b4 03 00 4c 89 f7 be 03 00 00 00 5b 41 5e 41
RSP: 0018:ffffc900179e7a68 EFLAGS: 00010293
RAX: ffffffff81be1b32 RBX: ffff888075ae0810 RCX: ffff88802f758000
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 0000000000000000
RBP: 00000000ffffffff R08: ffff888075ae097b R09: 1ffff1100eb5c12f
R10: dffffc0000000000 R11: ffffed100eb5c130 R12: dffffc0000000000
R13: 0000000000000000 R14: ffff888075ae0978 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff888125b79000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c3ee428 CR3: 0000000075a66000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 free_nsproxy+0x13a/0x560 kernel/nsproxy.c:195
 do_exit+0x6b8/0x2300 kernel/exit.c:969
 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: 0033:0x7f224db8f6c9
Code: Unable to access opcode bytes at 0x7f224db8f69f.
RSP: 002b:00007f224e9e90e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f224dde5fa8 RCX: 00007f224db8f6c9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f224dde5fa8
RBP: 00007f224dde5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f224dde6038 R14: 00007ffdda9ff3c0 R15: 00007ffdda9ff4a8
 </TASK>


---
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