[syzbot] [fs?] WARNING in destroy_super_work

[syzbot] [fs?] WARNING in destroy_super_work

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    982312090977 Add linux-next specific files for 20251103
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=17b2932f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=43cc0e31558cb527
dashboard link: https://syzkaller.appspot.com/bug?extid=1957b26299cf3ff7890c
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=1347817c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/40058f8a830c/disk-98231209.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1d7f42e8639f/vmlinux-98231209.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d8bb0284f393/bzImage-98231209.xz

The issue was bisected to:

commit 3c9820d5c64aeaadea7ffe3a6bb99d019a5ff46a
Author: Christian Brauner <brauner@kernel.org>
Date:   Wed Oct 29 12:20:24 2025 +0000

    ns: add active reference count

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=101e9bcd980000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=121e9bcd980000
console output: https://syzkaller.appspot.com/x/log.txt?x=141e9bcd980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1957b26299cf3ff7890c@syzkaller.appspotmail.com
Fixes: 3c9820d5c64a ("ns: add active reference count")

------------[ cut here ]------------
WARNING: ./include/linux/ns_common.h:229 at __ns_ref_put include/linux/ns_common.h:229 [inline], CPU#0: kworker/0:6/6108
WARNING: ./include/linux/ns_common.h:229 at put_user_ns include/linux/user_namespace.h:189 [inline], CPU#0: kworker/0:6/6108
WARNING: ./include/linux/ns_common.h:229 at destroy_super_work+0x15c/0x1a0 fs/super.c:280, CPU#0: kworker/0:6/6108
Modules linked in:
CPU: 0 UID: 0 PID: 6108 Comm: kworker/0:6 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: events destroy_super_work
RIP: 0010:__ns_ref_put include/linux/ns_common.h:229 [inline]
RIP: 0010:put_user_ns include/linux/user_namespace.h:189 [inline]
RIP: 0010:destroy_super_work+0x15c/0x1a0 fs/super.c:280
Code: 90 63 ff 48 81 c3 a8 fc ff ff 48 89 df e8 ec 90 63 ff 4c 89 f7 5b 41 5c 41 5d 41 5e 41 5f 5d e9 8a 91 e1 ff e8 45 df 86 ff 90 <0f> 0b 90 e9 6d ff ff ff e8 37 df 86 ff 4c 89 e7 be 03 00 00 00 e8
RSP: 0018:ffffc900030d7a48 EFLAGS: 00010293
RAX: ffffffff823a294b RBX: ffff88805639c898 RCX: ffff88802ab59e80
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000000
RBP: 0000000000000004 R08: ffff88807477565b R09: 1ffff1100e8eeacb
R10: dffffc0000000000 R11: ffffed100e8eeacc R12: ffff888074775658
R13: dffffc0000000000 R14: ffff88805639c000 R15: ffff8880747754c8
FS:  0000000000000000(0000) GS:ffff888125eda000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c008044000 CR3: 0000000077ad4000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 process_one_work+0x94a/0x15d0 kernel/workqueue.c:3267
 process_scheduled_works kernel/workqueue.c:3350 [inline]
 worker_thread+0x9b0/0xee0 kernel/workqueue.c:3431
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x52d/0xa70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>


---
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If the report is already addressed, let syzbot know by replying with:
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#syz undup

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

[Christian Brauner]

On Thu, Nov 06, 2025 at 11:31:27PM -0800, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    982312090977 Add linux-next specific files for 20251103
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=17b2932f980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=43cc0e31558cb527
> dashboard link: https://syzkaller.appspot.com/bug?extid=1957b26299cf3ff7890c
> 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=1347817c580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/40058f8a830c/disk-98231209.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/1d7f42e8639f/vmlinux-98231209.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/d8bb0284f393/bzImage-98231209.xz
> 
> The issue was bisected to:
> 
> commit 3c9820d5c64aeaadea7ffe3a6bb99d019a5ff46a
> Author: Christian Brauner <brauner@kernel.org>
> Date:   Wed Oct 29 12:20:24 2025 +0000
> 
>     ns: add active reference count
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=101e9bcd980000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=121e9bcd980000
> console output: https://syzkaller.appspot.com/x/log.txt?x=141e9bcd980000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+1957b26299cf3ff7890c@syzkaller.appspotmail.com
> Fixes: 3c9820d5c64a ("ns: add active reference count")

#syz test: https://github.com/brauner/linux.git namespace-6.19.fixes

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

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+1957b26299cf3ff7890c@syzkaller.appspotmail.com
Tested-by: syzbot+1957b26299cf3ff7890c@syzkaller.appspotmail.com

Tested on:

commit:         241462cd ns: fixes for namespace iteration and active ..
git tree:       https://github.com/brauner/linux.git namespace-6.19.fixes
console output: https://syzkaller.appspot.com/x/log.txt?x=11e1517c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f1b1a45727d1f117
dashboard link: https://syzkaller.appspot.com/bug?extid=1957b26299cf3ff7890c
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.