Re: [PATCH v2 2/2] drm: Make Legacy Context access functions optional.

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, May 13, 2015 at 07:54:48AM +0100, Peter Antoine wrote:
> As these functions are only used by one driver and there are security holes
> in these functions. Make the functions optional.
> 
> These changes are based on the two patches:
>   commit c21eb21cb50d58e7cbdcb8b9e7ff68b85cfa5095
>   Author: Dave Airlie <airlied@redhat.com>
> 
> And the commit that the above patch reverts:
>   commit 7c510133d93dd6f15ca040733ba7b2891ed61fd1
>   Author: Daniel Vetter <daniel.vetter@ffwll.ch>
> 
> This should now turn off the context feature.
> 
> Issue: VIZ-5485
> Signed-off-by: Peter Antoine <peter.antoine@intel.com>

Please cc drm core patches to dri-devel. Review below.
-Daniel

> ---
>  drivers/gpu/drm/drm_context.c | 36 ++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/drm_drv.c     | 12 +++++++-----
>  2 files changed, 43 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_context.c b/drivers/gpu/drm/drm_context.c
> index 9b23525..574be2a 100644
> --- a/drivers/gpu/drm/drm_context.c
> +++ b/drivers/gpu/drm/drm_context.c
> @@ -53,6 +53,9 @@ struct drm_ctx_list {
>   */
>  void drm_legacy_ctxbitmap_free(struct drm_device * dev, int ctx_handle)
>  {
> +	if (!drm_core_check_feature(dev, DRIVER_KMS_LEGACY_CONTEXT))
> +		return -EINVAL;

This doesn't compile too well. Also like with the previous patch, drivers
without DRIVER_MODESET still need these ioctls.

> +
>  	mutex_lock(&dev->struct_mutex);
>  	idr_remove(&dev->ctx_idr, ctx_handle);
>  	mutex_unlock(&dev->struct_mutex);
> @@ -87,6 +90,9 @@ static int drm_legacy_ctxbitmap_next(struct drm_device * dev)
>   */
>  int drm_legacy_ctxbitmap_init(struct drm_device * dev)
>  {
> +	if (!drm_core_check_feature(dev, DRIVER_KMS_LEGACY_CONTEXT))
> +		return -EINVAL;

This is redundant with the check you've added around the caller. Looking
at other places wrapping callers of _legacy_ functions with these checks
is the more common pattern in drm.

> +
>  	idr_init(&dev->ctx_idr);
>  	return 0;
>  }
> @@ -101,6 +107,9 @@ int drm_legacy_ctxbitmap_init(struct drm_device * dev)
>   */
>  void drm_legacy_ctxbitmap_cleanup(struct drm_device * dev)
>  {
> +	if (!drm_core_check_feature(dev, DRIVER_KMS_LEGACY_CONTEXT))
> +		return -EINVAL;

Same issue with compiling. And probably better to move the check out into
callers.

> +
>  	mutex_lock(&dev->struct_mutex);
>  	idr_destroy(&dev->ctx_idr);
>  	mutex_unlock(&dev->struct_mutex);
> @@ -119,6 +128,9 @@ void drm_legacy_ctxbitmap_flush(struct drm_device *dev, struct drm_file *file)
>  {
>  	struct drm_ctx_list *pos, *tmp;
>  
> +	if (!drm_core_check_feature(dev, DRIVER_KMS_LEGACY_CONTEXT))
> +		return -EINVAL;

Same as above.

> +
>  	mutex_lock(&dev->ctxlist_mutex);
>  
>  	list_for_each_entry_safe(pos, tmp, &dev->ctxlist, head) {
> @@ -161,6 +173,9 @@ int drm_legacy_getsareactx(struct drm_device *dev, void *data,
>  	struct drm_local_map *map;
>  	struct drm_map_list *_entry;
>  
> +	if (!drm_core_check_feature(dev, DRIVER_KMS_LEGACY_CONTEXT))
> +		return -EINVAL;
> +
>  	mutex_lock(&dev->struct_mutex);
>  
>  	map = idr_find(&dev->ctx_idr, request->ctx_id);
> @@ -205,6 +220,9 @@ int drm_legacy_setsareactx(struct drm_device *dev, void *data,
>  	struct drm_local_map *map = NULL;
>  	struct drm_map_list *r_list = NULL;
>  
> +	if (!drm_core_check_feature(dev, DRIVER_KMS_LEGACY_CONTEXT))
> +		return -EINVAL;
> +
>  	mutex_lock(&dev->struct_mutex);
>  	list_for_each_entry(r_list, &dev->maplist, head) {
>  		if (r_list->map
> @@ -305,6 +323,9 @@ int drm_legacy_resctx(struct drm_device *dev, void *data,
>  	struct drm_ctx ctx;
>  	int i;
>  
> +	if (!drm_core_check_feature(dev, DRIVER_KMS_LEGACY_CONTEXT))
> +		return -EINVAL;
> +
>  	if (res->count >= DRM_RESERVED_CONTEXTS) {
>  		memset(&ctx, 0, sizeof(ctx));
>  		for (i = 0; i < DRM_RESERVED_CONTEXTS; i++) {
> @@ -335,6 +356,9 @@ int drm_legacy_addctx(struct drm_device *dev, void *data,
>  	struct drm_ctx_list *ctx_entry;
>  	struct drm_ctx *ctx = data;
>  
> +	if (!drm_core_check_feature(dev, DRIVER_KMS_LEGACY_CONTEXT))
> +		return -EINVAL;
> +
>  	ctx->handle = drm_legacy_ctxbitmap_next(dev);
>  	if (ctx->handle == DRM_KERNEL_CONTEXT) {
>  		/* Skip kernel's context and get a new one. */
> @@ -378,6 +402,9 @@ int drm_legacy_getctx(struct drm_device *dev, void *data,
>  {
>  	struct drm_ctx *ctx = data;
>  
> +	if (!drm_core_check_feature(dev, DRIVER_KMS_LEGACY_CONTEXT))
> +		return -EINVAL;
> +
>  	/* This is 0, because we don't handle any context flags */
>  	ctx->flags = 0;
>  
> @@ -400,6 +427,9 @@ int drm_legacy_switchctx(struct drm_device *dev, void *data,
>  {
>  	struct drm_ctx *ctx = data;
>  
> +	if (!drm_core_check_feature(dev, DRIVER_KMS_LEGACY_CONTEXT))
> +		return -EINVAL;
> +
>  	DRM_DEBUG("%d\n", ctx->handle);
>  	return drm_context_switch(dev, dev->last_context, ctx->handle);
>  }
> @@ -420,6 +450,9 @@ int drm_legacy_newctx(struct drm_device *dev, void *data,
>  {
>  	struct drm_ctx *ctx = data;
>  
> +	if (!drm_core_check_feature(dev, DRIVER_KMS_LEGACY_CONTEXT))
> +		return -EINVAL;
> +
>  	DRM_DEBUG("%d\n", ctx->handle);
>  	drm_context_switch_complete(dev, file_priv, ctx->handle);
>  
> @@ -442,6 +475,9 @@ int drm_legacy_rmctx(struct drm_device *dev, void *data,
>  {
>  	struct drm_ctx *ctx = data;
>  
> +	if (!drm_core_check_feature(dev, DRIVER_KMS_LEGACY_CONTEXT))
> +		return -EINVAL;
> +
>  	DRM_DEBUG("%d\n", ctx->handle);
>  	if (ctx->handle != DRM_KERNEL_CONTEXT) {
>  		if (dev->driver->context_dtor)
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 3b3c4f5..1de2df8 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -584,11 +584,13 @@ struct drm_device *drm_dev_alloc(struct drm_driver *driver,
>  	if (drm_ht_create(&dev->map_hash, 12))
>  		goto err_minors;
>  
> -	ret = drm_legacy_ctxbitmap_init(dev);
> -	if (ret) {
> -		DRM_ERROR("Cannot allocate memory for context bitmap.\n");
> -		goto err_ht;
> -	}
> +	if (drm_core_check_feature(dev, DRIVER_KMS_LEGACY_CONTEXT))

Coding style requires {} since it's multi-line. And confusing since the if
(ret) gets always executed.

> +		ret = drm_legacy_ctxbitmap_init(dev);
> +		if (ret) {
> +			DRM_ERROR(
> +				"Cannot allocate memory for context bitmap.\n");
> +			goto err_ht;
> +		}
>  
>  	if (drm_core_check_feature(dev, DRIVER_GEM)) {
>  		ret = drm_gem_init(dev);
> -- 
> 1.9.1
> 

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