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Subject: Re: [PATCH] nv50_disp_chan_mthd: ensure mthd is not NULL
From:   =?UTF-8?B?RnLDqWTDqXJpYyBQaWVycmV0?= 
        <frederic.pierret@qubes-os.org>
To:     bskeggs@redhat.com, airlied@linux.ie, daniel@ffwll.ch,
        dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org,
        linux-kernel@vger.kernel.org
References: <dac89843-5258-5bed-ee86-7038e94e56da@qubes-os.org>
Message-ID: <c94ce223-56d5-e31a-2a2c-59defb988b28@qubes-os.org>
Date:   Thu, 20 Feb 2020 18:19:24 +0100
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Hi,
Is anything missing here? How can I get this merged?

Best regards,
Fr=C3=A9d=C3=A9ric Pierret

On 2020-02-08 20:43, Fr=C3=A9d=C3=A9ric Pierret wrote:
> Pointer to structure array is assumed not NULL by default. It has
> the consequence to raise a kernel panic when it's not the case.
>=20
> Basically, running at least a RTX2080TI on Xen makes a bad mmio error
> which causes having 'mthd' pointer to be NULL in 'channv50.c'. From the=

> code, it's assumed to be not NULL by accessing directly 'mthd->data[0]'=

> which is the reason of the kernel panic. Simply check if the pointer
> is not NULL before continuing.
>=20
> BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=3D206299
> Cc: stable@vger.kernel.org
> Signed-off-by: Fr=C3=A9d=C3=A9ric Pierret (fepitre) <frederic.pierret@q=
ubes-os.org>
> ---
>  drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c | 2 ++
>  1 file changed, 2 insertions(+)
>=20
> diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c b/driv=
ers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c
> index bcf32d92ee5a..50e3539f33d2 100644
> --- a/drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c
> +++ b/drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c
> @@ -74,6 +74,8 @@ nv50_disp_chan_mthd(struct nv50_disp_chan *chan, int =
debug)
> =20
>  	if (debug > subdev->debug)
>  		return;
> +	if (!mthd)
> +		return;
> =20
>  	for (i =3D 0; (list =3D mthd->data[i].mthd) !=3D NULL; i++) {
>  		u32 base =3D chan->head * mthd->addr;
>=20


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