[PATCH] drm/vkms: Hold gem object while still in-use

[Rodrigo Siqueira]

Thanks for your patch!

Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira at amd.com>

On 04/27, Ezequiel Garcia wrote:
> We need to keep the reference to the drm_gem_object
> until the last access by vkms_dumb_create.
> 
> Therefore, the put the object after it is used.
> 
> This fixes a use-after-free issue reported by syzbot.
> 
> While here, change vkms_gem_create() symbol to static.
> 
> Reported-and-tested-by: syzbot+e3372a2afe1e7ef04bc7 at syzkaller.appspotmail.com
> Signed-off-by: Ezequiel Garcia <ezequiel at collabora.com>
> ---
>  drivers/gpu/drm/vkms/vkms_drv.h |  5 -----
>  drivers/gpu/drm/vkms/vkms_gem.c | 11 ++++++-----
>  2 files changed, 6 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> index eda04ffba7b1..f4036bb0b9a8 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.h
> +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> @@ -117,11 +117,6 @@ struct drm_plane *vkms_plane_init(struct vkms_device *vkmsdev,
>  				  enum drm_plane_type type, int index);
>  
>  /* Gem stuff */
> -struct drm_gem_object *vkms_gem_create(struct drm_device *dev,
> -				       struct drm_file *file,
> -				       u32 *handle,
> -				       u64 size);
> -
>  vm_fault_t vkms_gem_fault(struct vm_fault *vmf);
>  
>  int vkms_dumb_create(struct drm_file *file, struct drm_device *dev,
> diff --git a/drivers/gpu/drm/vkms/vkms_gem.c b/drivers/gpu/drm/vkms/vkms_gem.c
> index 2e01186fb943..c541fec57566 100644
> --- a/drivers/gpu/drm/vkms/vkms_gem.c
> +++ b/drivers/gpu/drm/vkms/vkms_gem.c
> @@ -97,10 +97,10 @@ vm_fault_t vkms_gem_fault(struct vm_fault *vmf)
>  	return ret;
>  }
>  
> -struct drm_gem_object *vkms_gem_create(struct drm_device *dev,
> -				       struct drm_file *file,
> -				       u32 *handle,
> -				       u64 size)
> +static struct drm_gem_object *vkms_gem_create(struct drm_device *dev,
> +					      struct drm_file *file,
> +					      u32 *handle,
> +					      u64 size)
>  {
>  	struct vkms_gem_object *obj;
>  	int ret;
> @@ -113,7 +113,6 @@ struct drm_gem_object *vkms_gem_create(struct drm_device *dev,
>  		return ERR_CAST(obj);
>  
>  	ret = drm_gem_handle_create(file, &obj->gem, handle);
> -	drm_gem_object_put_unlocked(&obj->gem);
>  	if (ret)
>  		return ERR_PTR(ret);
>  
> @@ -142,6 +141,8 @@ int vkms_dumb_create(struct drm_file *file, struct drm_device *dev,
>  	args->size = gem_obj->size;
>  	args->pitch = pitch;
>  
> +	drm_gem_object_put_unlocked(gem_obj);
> +
>  	DRM_DEBUG_DRIVER("Created object of size %lld\n", size);
>  
>  	return 0;
> -- 
> 2.26.0.rc2
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel at lists.freedesktop.org

-- 
Rodrigo Siqueira
https://siqueira.tech
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