linux-kernel - Re: [syzbot] [mm?] WARNING: lock held when returning to user space in lock_next

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Message-ID: <CAJuCfpFjLmDRE=3E91279A+diisTgz24+a5D6c+sH8Oh7PzP6g@mail.gmail.com>
Date: Tue, 8 Jul 2025 15:19:18 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: syzbot <syzbot+80011ad33eec39e6ce42@...kaller.appspotmail.com>
Cc: Liam.Howlett@...cle.com, akpm@...ux-foundation.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, lorenzo.stoakes@...cle.com, 
	shakeel.butt@...ux.dev, syzkaller-bugs@...glegroups.com, vbabka@...e.cz
Subject: Re: [syzbot] [mm?] WARNING: lock held when returning to user space in lock_next_vma

On Tue, Jul 8, 2025 at 10:52 AM syzbot
<syzbot+80011ad33eec39e6ce42@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    26ffb3d6f02c Add linux-next specific files for 20250704
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=1719df70580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=1e4f88512ae53408
> dashboard link: https://syzkaller.appspot.com/bug?extid=80011ad33eec39e6ce42
> compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1124abd4580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1099df70580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/fd5569903143/disk-26ffb3d6.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/1b0c9505c543/vmlinux-26ffb3d6.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/9d864c72bed1/bzImage-26ffb3d6.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+80011ad33eec39e6ce42@...kaller.appspotmail.com
>
> ================================================
> WARNING: lock held when returning to user space!
> 6.16.0-rc4-next-20250704-syzkaller #0 Not tainted
> ------------------------------------------------
> syz.0.22/6068 is leaving the kernel with locks still held!
> 1 lock held by syz.0.22/6068:
>  #0: ffff8880792a3588 (vm_lock){++++}-{0:0}, at: lock_next_vma+0x146/0xdc0 mm/mmap_lock.c:220

Hmm. I must be missing an unlock_vma() somewhere but I don't see it
yet. Will try the reproducer.

>
>
> ---
> 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@...glegroups.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:
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>
> 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:
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>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
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