From: Marc Zyngier <maz@kernel.org>
To: syzbot <syzbot+c41f3ddb8299a30a98b5@syzkaller.appspotmail.com>
Cc: catalin.marinas@arm.com, joey.gouly@arm.com,
kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, oliver.upton@linux.dev,
suzuki.poulose@arm.com, syzkaller-bugs@googlegroups.com,
will@kernel.org, yuzenghui@huawei.com
Subject: Re: [syzbot] [kvmarm?] kernel BUG in kvm_s2_put_page
Date: Fri, 19 Sep 2025 15:26:58 +0100 [thread overview]
Message-ID: <871po2zff1.wl-maz@kernel.org> (raw)
In-Reply-To: <68cd66b0.050a0220.139b6.000f.GAE@google.com>
On Fri, 19 Sep 2025 15:20:32 +0100,
syzbot <syzbot+c41f3ddb8299a30a98b5@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 62e68218ab58 Merge branch kvm-arm64/nv-debug into kvmarm-m..
> git tree: git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next
> console output: https://syzkaller.appspot.com/x/log.txt?x=1551cf62580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=1b1bafe30fc85201
> dashboard link: https://syzkaller.appspot.com/bug?extid=c41f3ddb8299a30a98b5
> compiler: Debian clang version 20.1.8 (++20250708123704+0de59a293f7a-1~exp1~20250708003721.134), Debian LLD 20.1.8
> userspace arch: arm64
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/fa3fbcfdac58/non_bootable_disk-62e68218.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/99c4e665c20d/vmlinux-62e68218.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/4204d63db4b5/Image-62e68218.gz.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+c41f3ddb8299a30a98b5@syzkaller.appspotmail.com
>
> raw: 01ffea8000000000 ffffc1ffc0807c48 ffffc1ffc080a888 0000000000000000
> raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
> page dumped because: VM_BUG_ON_PAGE(page_ref_count(page) == 0)
> ------------[ cut here ]------------
> kernel BUG at ./include/linux/mm.h:1036!
> Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
> Modules linked in:
> CPU: 0 UID: 0 PID: 4079 Comm: syz.1.200 Not tainted syzkaller #0 PREEMPT
> Hardware name: linux,dummy-virt (DT)
> pstate: 60402009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : put_page_testzero include/linux/mm.h:1036 [inline]
> pc : folio_put_testzero include/linux/mm.h:1042 [inline]
> pc : folio_put include/linux/mm.h:1359 [inline]
> pc : put_page include/linux/mm.h:1429 [inline]
> pc : kvm_s2_put_page+0x374/0x3a0 arch/arm64/kvm/mmu.c:264
> lr : put_page_testzero include/linux/mm.h:1036 [inline]
> lr : folio_put_testzero include/linux/mm.h:1042 [inline]
> lr : folio_put include/linux/mm.h:1359 [inline]
> lr : put_page include/linux/mm.h:1429 [inline]
> lr : kvm_s2_put_page+0x374/0x3a0 arch/arm64/kvm/mmu.c:264
This is likely caused by the S2 refcounting issue that has just been
reverted in Linus' tree, and that is not in the kvmarm/next branch.
M.
--
Jazz isn't dead. It just smells funny.
next prev parent reply other threads:[~2025-09-19 14:27 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-19 14:20 [syzbot] [kvmarm?] kernel BUG in kvm_s2_put_page syzbot
2025-09-19 14:26 ` Marc Zyngier [this message]
2025-10-29 20:04 ` syzbot
2025-10-29 20:27 ` Oliver Upton
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