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

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Message-ID: <6mw4p4shg6myw5a677hkvhzytsnfa2e5zb7zpe6kcqlfjglmol@pzwcbowwy2v5>
Date: Tue, 8 Jul 2025 19:15:13 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: syzbot <syzbot+80011ad33eec39e6ce42@...kaller.appspotmail.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

* Suren Baghdasaryan <surenb@...gle.com> [250708 18:19]:
> 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.

The last one was against v5 patches, is this v6?