From: Johan Hovold <johan@kernel•org>
To: Jason Wang <jasowang@redhat•com>
Cc: "Michael S . Tsirkin" <mst@redhat•com>,
"Xuan Zhuo" <xuanzhuo@linux•alibaba.com>,
"Eugenio Pérez" <eperezma@redhat•com>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation•org>,
virtualization@lists•linux.dev, linux-kernel@vger•kernel.org,
stable@vger•kernel.org, "Pawel Moll" <pawel.moll@arm•com>
Subject: Re: [PATCH] virtio-mmio: fix device release warning on module unload
Date: Mon, 27 Apr 2026 17:01:58 +0200 [thread overview]
Message-ID: <ae96Zsike81dBxTS@hovoldconsulting.com> (raw)
In-Reply-To: <CACGkMEvJ4CZt9mVhn5TRCz5yCYzY_yHNFh8pbT4hOmJoWDiKOA@mail.gmail.com>
On Mon, Apr 27, 2026 at 12:16:47PM +0800, Jason Wang wrote:
> On Fri, Apr 24, 2026 at 6:48 PM Johan Hovold <johan@kernel•org> wrote:
> >
> > Driver core expects devices to be allocated dynamically and complains
> > loudly when a device that lacks a release function is freed.
> >
> > Use __root_device_register() to allocate and register the root device
> > instead of open coding using a static device.
> > -static struct device vm_cmdline_parent = {
> > - .init_name = "virtio-mmio-cmdline",
> > -};
> > +static struct device *vm_cmdline_parent;
>
> vm_cmdline_get() is the .get callback for the device module parameter.
> It is invoked when userspace reads
> /sys/module/virtio_mmio/parameters/device. This function uses
> vm_cmdline_parent unconditionally, without checking whether the device
> has been registered. This would cause NULL pointer dereference.
Indeed, Sashiko flagged this as well. Just sent a v2 here:
https://lore.kernel.org/r/20260427143710.14702-1-johan@kernel.org
Johan
prev parent reply other threads:[~2026-04-27 15:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-24 10:48 [PATCH] virtio-mmio: fix device release warning on module unload Johan Hovold
2026-04-27 4:16 ` Jason Wang
2026-04-27 15:01 ` Johan Hovold [this message]
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