[PATCH] drm/via: Add new condition to via_dma_cleanup()

[PATCH] drm/via: Add new condition to via_dma_cleanup()

[Alisa Khabibrakhmanova]

Pointer dev_priv->mmio, which was checked for NULL at via_do_init_map(),
is passed to via_do_cleanup_map() and is dereferenced there without check.

The patch adds the condition in via_dma_cleanup() which prevents potential NULL
pointer dereference.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 22f579c621e2 ("drm: Add via unichrome support")
Signed-off-by: Alisa Khabibrakhmanova <khabibrakhmanova@ispras.ru>
---
 drivers/gpu/drm/via/via_dma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/via/via_dma.c b/drivers/gpu/drm/via/via_dma.c
index 177b0499abf1..56bcbbf4ed54 100644
--- a/drivers/gpu/drm/via/via_dma.c
+++ b/drivers/gpu/drm/via/via_dma.c
@@ -164,7 +164,7 @@ int via_dma_cleanup(struct drm_device *dev)
 		drm_via_private_t *dev_priv =
 		    (drm_via_private_t *) dev->dev_private;
 
-		if (dev_priv->ring.virtual_start) {
+		if (dev_priv->ring.virtual_start && dev_priv->mmio) {
 			via_cmdbuf_reset(dev_priv);
 
 			drm_legacy_ioremapfree(&dev_priv->ring.map, dev);
-- 
2.34.1

Re: [PATCH] drm/via: Add new condition to via_dma_cleanup()

[Sam Ravnborg]

Hi Alisa,

On Mon, Jul 25, 2022 at 01:45:55PM +0300, Alisa Khabibrakhmanova wrote:
> Pointer dev_priv->mmio, which was checked for NULL at via_do_init_map(),
> is passed to via_do_cleanup_map() and is dereferenced there without check.
> 
> The patch adds the condition in via_dma_cleanup() which prevents potential NULL
> pointer dereference.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: 22f579c621e2 ("drm: Add via unichrome support")
> Signed-off-by: Alisa Khabibrakhmanova <khabibrakhmanova@ispras.ru>

Thanks for your patch. Due to other changes in drm-misc where we
maintain the via driver this patch fails to apply.
It would be great if you could redo the patch after -rc2 - on top of
-next. Then we can apply it to drm-misc.

You will see that the individual files for the driver is merged to a
single file, and this change does not hit -next until later.

	Sam

[PATCH] drm/via: Add new condition to via_dma_cleanup()

[Alisa Khabibrakhmanova]

Pointer dev_priv->mmio, which was checked for NULL at via_do_init_map(),
is passed to via_do_cleanup_map() and is dereferenced there without check.

The patch adds the condition in via_dma_cleanup() which prevents potential NULL
pointer dereference.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 22f579c621e2 ("drm: Add via unichrome support")
Signed-off-by: Alisa Khabibrakhmanova <khabibrakhmanova@ispras.ru>
---
 drivers/gpu/drm/via/via_dri1.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/via/via_dri1.c b/drivers/gpu/drm/via/via_dri1.c
index d695d9291ece..691e3ceb0062 100644
--- a/drivers/gpu/drm/via/via_dri1.c
+++ b/drivers/gpu/drm/via/via_dri1.c
@@ -2961,7 +2961,7 @@ int via_dma_cleanup(struct drm_device *dev)
 		drm_via_private_t *dev_priv =
 		    (drm_via_private_t *) dev->dev_private;
 
-		if (dev_priv->ring.virtual_start) {
+		if (dev_priv->ring.virtual_start && dev_priv->mmio) {
 			via_cmdbuf_reset(dev_priv);
 
 			drm_legacy_ioremapfree(&dev_priv->ring.map, dev);
-- 
2.34.1

Re: [PATCH] drm/via: Add new condition to via_dma_cleanup()

[Daniel Vetter]

On Fri, Jul 29, 2022 at 12:06:43PM +0300, Alisa Khabibrakhmanova wrote:
> Pointer dev_priv->mmio, which was checked for NULL at via_do_init_map(),
> is passed to via_do_cleanup_map() and is dereferenced there without check.
> 
> The patch adds the condition in via_dma_cleanup() which prevents potential NULL
> pointer dereference.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: 22f579c621e2 ("drm: Add via unichrome support")
> Signed-off-by: Alisa Khabibrakhmanova <khabibrakhmanova@ispras.ru>

This seems to have fallen through cracks, I applied it to drm-misc-next
now.

Thanks for your patch.
-Daniel

> ---
>  drivers/gpu/drm/via/via_dri1.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/via/via_dri1.c b/drivers/gpu/drm/via/via_dri1.c
> index d695d9291ece..691e3ceb0062 100644
> --- a/drivers/gpu/drm/via/via_dri1.c
> +++ b/drivers/gpu/drm/via/via_dri1.c
> @@ -2961,7 +2961,7 @@ int via_dma_cleanup(struct drm_device *dev)
>  		drm_via_private_t *dev_priv =
>  		    (drm_via_private_t *) dev->dev_private;
>  
> -		if (dev_priv->ring.virtual_start) {
> +		if (dev_priv->ring.virtual_start && dev_priv->mmio) {
>  			via_cmdbuf_reset(dev_priv);
>  
>  			drm_legacy_ioremapfree(&dev_priv->ring.map, dev);
> -- 
> 2.34.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch