Nouveau - Feb 2020 - [PATCH] nv50_disp_chan_mthd: ensure mthd is not NULL

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.

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.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=206299
Cc: stable at vger.kernel.org
Signed-off-by: Fr?d?ric Pierret (fepitre) <frederic.pierret at
qubes-os.org>
---
 drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c
b/drivers/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)
 
 	if (debug > subdev->debug)
 		return;
+	if (!mthd)
+		return;
 
 	for (i = 0; (list = mthd->data[i].mthd) != NULL; i++) {
 		u32 base = chan->head * mthd->addr;
-- 
2.21.0


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Hi,
Is anything missing here? How can I get this merged?

Best regards,
Fr?d?ric Pierret

On 2020-02-08 20:43, Fr?d?ric 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.
> 
> 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.
> 
> BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=206299
> Cc: stable at vger.kernel.org
> Signed-off-by: Fr?d?ric Pierret (fepitre) <frederic.pierret at
qubes-os.org>
> ---
>  drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c
b/drivers/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)
>  
>  	if (debug > subdev->debug)
>  		return;
> +	if (!mthd)
> +		return;
>  
>  	for (i = 0; (list = mthd->data[i].mthd) != NULL; i++) {
>  		u32 base = chan->head * mthd->addr;
> 
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Hi Fr?d?ric,

It appears Ben made his own version of this patch (probably based on
the one you added to the kernel bz), and it's already upstream:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.6-rc2&id=0e6176c6d286316e9431b4f695940cfac4ffe6c2

Cheers,

  -ilia

On Thu, Feb 20, 2020 at 12:19 PM Fr?d?ric Pierret
<frederic.pierret at qubes-os.org> wrote:
>
> Hi,
> Is anything missing here? How can I get this merged?
>
> Best regards,
> Fr?d?ric Pierret
>
> On 2020-02-08 20:43, Fr?d?ric 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.
> >
> > 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.
> >
> > BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=206299
> > Cc: stable at vger.kernel.org
> > Signed-off-by: Fr?d?ric Pierret (fepitre) <frederic.pierret at
qubes-os.org>
> > ---
> >  drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/disp/channv50.c
b/drivers/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)
> >
> >       if (debug > subdev->debug)
> >               return;
> > +     if (!mthd)
> > +             return;
> >
> >       for (i = 0; (list = mthd->data[i].mthd) != NULL; i++) {
> >               u32 base = chan->head * mthd->addr;
> >
>
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