linux-kernel - Re: [PATCH 1/1] video: hyperv_fb: Fix validation of screen resolution

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Message-ID: <20220124133119.3yxfr7ypmmdotm6h@liuwe-devbox-debian-v2>
Date:   Mon, 24 Jan 2022 13:31:19 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Helge Deller <deller@....de>
Cc:     Wei Liu <wei.liu@...nel.org>,
        "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Hu <weh@...rosoft.com>, Dexuan Cui <decui@...rosoft.com>,
        "drawat.floss@...il.com" <drawat.floss@...il.com>,
        hhei <hhei@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH 1/1] video: hyperv_fb: Fix validation of screen resolution

On Mon, Jan 24, 2022 at 10:52:22AM +0100, Helge Deller wrote:
> On 1/23/22 23:30, Wei Liu wrote:
> > On Sun, Jan 23, 2022 at 10:27:56PM +0000, Michael Kelley (LINUX) wrote:
> >> From: Wei Liu <wei.liu@...nel.org> Sent: Sunday, January 23, 2022 1:56 PM
> >>>
> >>> On Sun, Jan 16, 2022 at 09:53:06PM +0000, Haiyang Zhang wrote:
> >>>>
> >>>>
> >>>>> -----Original Message-----
> >>>>> From: Michael Kelley (LINUX) <mikelley@...rosoft.com>
> >>>>> Sent: Sunday, January 16, 2022 2:19 PM
> >>>>> To: KY Srinivasan <kys@...rosoft.com>; Haiyang Zhang
> >>> <haiyangz@...rosoft.com>; Stephen
> >>>>> Hemminger <sthemmin@...rosoft.com>; wei.liu@...nel.org; Wei Hu
> >>> <weh@...rosoft.com>; Dexuan
> >>>>> Cui <decui@...rosoft.com>; drawat.floss@...il.com; hhei <hhei@...hat.com>;
> >>> linux-
> >>>>> kernel@...r.kernel.org; linux-hyperv@...r.kernel.org; linux-
> >>> fbdev@...r.kernel.org; dri-
> >>>>> devel@...ts.freedesktop.org
> >>>>> Cc: Michael Kelley (LINUX) <mikelley@...rosoft.com>
> >>>>> Subject: [PATCH 1/1] video: hyperv_fb: Fix validation of screen resolution
> >>>>>
> >>>>> In the WIN10 version of the Synthetic Video protocol with Hyper-V,
> >>>>> Hyper-V reports a list of supported resolutions as part of the protocol
> >>>>> negotiation. The driver calculates the maximum width and height from
> >>>>> the list of resolutions, and uses those maximums to validate any screen
> >>>>> resolution specified in the video= option on the kernel boot line.
> >>>>>
> >>>>> This method of validation is incorrect. For example, the list of
> >>>>> supported resolutions could contain 1600x1200 and 1920x1080, both of
> >>>>> which fit in an 8 Mbyte frame buffer.  But calculating the max width
> >>>>> and height yields 1920 and 1200, and 1920x1200 resolution does not fit
> >>>>> in an 8 Mbyte frame buffer.  Unfortunately, this resolution is accepted,
> >>>>> causing a kernel fault when the driver accesses memory outside the
> >>>>> frame buffer.
> >>>>>
> >>>>> Instead, validate the specified screen resolution by calculating
> >>>>> its size, and comparing against the frame buffer size.  Delete the
> >>>>> code for calculating the max width and height from the list of
> >>>>> resolutions, since these max values have no use.  Also add the
> >>>>> frame buffer size to the info message to aid in understanding why
> >>>>> a resolution might be rejected.
> >>>>>
> >>>>> Fixes: 67e7cdb4829d ("video: hyperv: hyperv_fb: Obtain screen resolution from Hyper-V
> >>>>> host")
> >>>>> Signed-off-by: Michael Kelley <mikelley@...rosoft.com>
> >>> [...]
> >>>>
> >>>> Reviewed-by: Haiyang Zhang <haiyangz@...rosoft.com>
> >>>>
> >>>
> >>> Applied to hyperv-fixes. Thanks.
> >>
> >> This fix got pulled into the fbdev/for-next tree by a new maintainer, Helge Deller.
> >> See https://git.kernel.org/pub/scm/linux/kernel/git/deller/linux-fbdev.git/commit/?h=for-next&id=bcc48f8d980b12e66a3d59dfa1041667db971d86
> >
> > OK. I will drop it from hyperv-fixes. Thanks for letting me know!
> 
> Linus hasn't pulled my tree yet, and he will probably not before the
> next merge window. So, if this is an urgent bugfix for you, I can offer
> to drop it from the fbdev tree and that you take it through the hyperv-fixes tree.
> In that case you may add an Acked-by: Helge Deller <deller@....de>.
> Just let me know what you prefer.

Hi Helge

Yes, I would like to upstream it as soon as possible so that it can
propagate to stable trees and be backported by downstream vendors.

I will pick it up in hyperv-fixes. Please drop it from your for-next
tree.

Thanks,
Wei.

> 
> Helge