[PATCH] gpu: radeon: fix a potential NULL-pointer dereference

[PATCH] gpu: radeon: fix a potential NULL-pointer dereference

[Kangjie Lu]

In case alloc_workqueue fails, the fix frees memory and
returns to avoid potential NULL pointer dereference.

Signed-off-by: Kangjie Lu <kjlu@umn.edu>
---
 drivers/gpu/drm/radeon/radeon_display.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
index aa898c699101..a31305755a77 100644
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -678,6 +678,11 @@ static void radeon_crtc_init(struct drm_device *dev, int index)
 	drm_mode_crtc_set_gamma_size(&radeon_crtc->base, 256);
 	radeon_crtc->crtc_id = index;
 	radeon_crtc->flip_queue = alloc_workqueue("radeon-crtc", WQ_HIGHPRI, 0);
+	if (!radeon_crtc->flip_queue) {
+		DRM_ERROR("failed to allocate the flip queue\n");
+		kfree(radeon_crtc);
+		return;
+	}
 	rdev->mode_info.crtcs[index] = radeon_crtc;
 
 	if (rdev->family >= CHIP_BONAIRE) {
-- 
2.17.1

Re: [PATCH] gpu: radeon: fix a potential NULL-pointer dereference

[Michel Dänzer]

Hi Kangjie,


thanks for your patch.


On 2019-03-23 3:29 a.m., Kangjie Lu wrote:
> In case alloc_workqueue fails, the fix frees memory and
> returns to avoid potential NULL pointer dereference.
> 
> Signed-off-by: Kangjie Lu <kjlu@umn.edu>
> ---
>  drivers/gpu/drm/radeon/radeon_display.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
> index aa898c699101..a31305755a77 100644
> --- a/drivers/gpu/drm/radeon/radeon_display.c
> +++ b/drivers/gpu/drm/radeon/radeon_display.c
> @@ -678,6 +678,11 @@ static void radeon_crtc_init(struct drm_device *dev, int index)
>  	drm_mode_crtc_set_gamma_size(&radeon_crtc->base, 256);
>  	radeon_crtc->crtc_id = index;
>  	radeon_crtc->flip_queue = alloc_workqueue("radeon-crtc", WQ_HIGHPRI, 0);
> +	if (!radeon_crtc->flip_queue) {
> +		DRM_ERROR("failed to allocate the flip queue\n");
> +		kfree(radeon_crtc);

This would leak some memory referenced by struct drm_crtc. To solve
this, I suggest calling radeon_crtc_destroy here and making that cope
with radeon_crtc->flip_queue being NULL.


Also, I'm not sure all driver code can handle some CRTCs not
initializing. Given that, and as alloc_workqueue presumably only fails
if the system is essentially out of memory anyway, it's probably better
for radeon_crtc_init to return -ENOMEM in this case and for
radeon_modeset_init to propagate that, which will prevent the driver as
a whole from initializing.


-- 
Earthling Michel Dänzer               |              https://www.amd.com
Libre software enthusiast             |             Mesa and X developer

[PATCH v2] gpu: radeon: fix a potential NULL-pointer dereference

[Kangjie Lu]

In case alloc_workqueue fails, the fix frees memory and
returns -ENOMEM to avoid potential NULL pointer dereference.

Signed-off-by: Kangjie Lu <kjlu@umn.edu>
---
v2: use radeon_crtc_destroy to properly clean up resources as
suggested by Michel Dänzer <michel@daenzer.net>
---
 drivers/gpu/drm/radeon/radeon_display.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
index aa898c699101..3c6d3289316b 100644
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -663,7 +663,7 @@ static const struct drm_crtc_funcs radeon_crtc_funcs = {
 	.page_flip_target = radeon_crtc_page_flip_target,
 };
 
-static void radeon_crtc_init(struct drm_device *dev, int index)
+static int radeon_crtc_init(struct drm_device *dev, int index)
 {
 	struct radeon_device *rdev = dev->dev_private;
 	struct radeon_crtc *radeon_crtc;
@@ -671,13 +671,18 @@ static void radeon_crtc_init(struct drm_device *dev, int index)
 
 	radeon_crtc = kzalloc(sizeof(struct radeon_crtc) + (RADEONFB_CONN_LIMIT * sizeof(struct drm_connector *)), GFP_KERNEL);
 	if (radeon_crtc == NULL)
-		return;
+		return -ENOMEM;
 
 	drm_crtc_init(dev, &radeon_crtc->base, &radeon_crtc_funcs);
 
 	drm_mode_crtc_set_gamma_size(&radeon_crtc->base, 256);
 	radeon_crtc->crtc_id = index;
 	radeon_crtc->flip_queue = alloc_workqueue("radeon-crtc", WQ_HIGHPRI, 0);
+	if (!radeon_crtc->flip_queue) {
+		DRM_ERROR("failed to allocate the flip queue\n");
+		radeon_crtc_destroy(&radeon_crtc->base);
+		return -ENOMEM;
+	}
 	rdev->mode_info.crtcs[index] = radeon_crtc;
 
 	if (rdev->family >= CHIP_BONAIRE) {
@@ -706,6 +711,8 @@ static void radeon_crtc_init(struct drm_device *dev, int index)
 		radeon_atombios_init_crtc(dev, radeon_crtc);
 	else
 		radeon_legacy_init_crtc(dev, radeon_crtc);
+
+	return 0;
 }
 
 static const char *encoder_names[38] = {
@@ -1612,7 +1619,9 @@ int radeon_modeset_init(struct radeon_device *rdev)
 
 	/* allocate crtcs */
 	for (i = 0; i < rdev->num_crtc; i++) {
-		radeon_crtc_init(rdev->ddev, i);
+		ret = radeon_crtc_init(rdev->ddev, i);
+		if (ret)
+			return ret;
 	}
 
 	/* okay we should have all the bios connectors */
-- 
2.17.1

Re: [PATCH v2] gpu: radeon: fix a potential NULL-pointer dereference

[Michel Dänzer]

On 2019-03-25 10:05 p.m., Kangjie Lu wrote:
> In case alloc_workqueue fails, the fix frees memory and
> returns -ENOMEM to avoid potential NULL pointer dereference.
> 
> Signed-off-by: Kangjie Lu <kjlu@umn.edu>
> ---
> v2: use radeon_crtc_destroy to properly clean up resources as
> suggested by Michel Dänzer <michel@daenzer.net>
> 
>  [...]
> 
> @@ -671,13 +671,18 @@ static void radeon_crtc_init(struct drm_device *dev, int index)
>  
>  	radeon_crtc = kzalloc(sizeof(struct radeon_crtc) + (RADEONFB_CONN_LIMIT * sizeof(struct drm_connector *)), GFP_KERNEL);
>  	if (radeon_crtc == NULL)
> -		return;
> +		return -ENOMEM;
>  
>  	drm_crtc_init(dev, &radeon_crtc->base, &radeon_crtc_funcs);
>  
>  	drm_mode_crtc_set_gamma_size(&radeon_crtc->base, 256);
>  	radeon_crtc->crtc_id = index;
>  	radeon_crtc->flip_queue = alloc_workqueue("radeon-crtc", WQ_HIGHPRI, 0);
> +	if (!radeon_crtc->flip_queue) {
> +		DRM_ERROR("failed to allocate the flip queue\n");
> +		radeon_crtc_destroy(&radeon_crtc->base);
> +		return -ENOMEM;
> +	}

radeon_crtc_destroy currently unconditionally calls:

	destroy_workqueue(radeon_crtc->flip_queue);

AFAICT destroy_workqueue will blow up if NULL is passed to it, so
radeon_crtc_destroy needs to check for that.


-- 
Earthling Michel Dänzer               |              https://www.amd.com
Libre software enthusiast             |             Mesa and X developer