On 07/14/2015 02:20 PM, Thierry Reding wrote:
> On Mon, Jul 13, 2015 at 12:08:08PM +0530, Archit Taneja wrote:
> [...]
>> diff --git a/drivers/gpu/drm/tegra/fb.c b/drivers/gpu/drm/tegra/fb.c
> [...]
>> @@ -224,11 +224,11 @@ static int tegra_fbdev_probe(struct drm_fb_helper
>> *helper,
>> if (IS_ERR(bo))
>> return PTR_ERR(bo);
>>
>> - info = framebuffer_alloc(0, drm->dev);
>> - if (!info) {
>> + info = drm_fb_helper_alloc_fbi(helper);
>> + if (IS_ERR(info)) {
>> dev_err(drm->dev, "failed to allocate framebuffer info\n");
>> - drm_gem_object_unreference_unlocked(&bo->gem);
>> - return -ENOMEM;
>> + err = PTR_ERR(info);
>> + goto gem_unref;
>> }
>>
>> fbdev->fb = tegra_fb_alloc(drm, &cmd, &bo, 1);
>> @@ -236,7 +236,6 @@ static int tegra_fbdev_probe(struct drm_fb_helper
>> *helper,
>> err = PTR_ERR(fbdev->fb);
>> dev_err(drm->dev, "failed to allocate DRM framebuffer: %d\n",
>> err);
>> - drm_gem_object_unreference_unlocked(&bo->gem);
>> goto release;
>> }
>>
>> @@ -248,12 +247,6 @@ static int tegra_fbdev_probe(struct drm_fb_helper
>> *helper,
>> info->flags = FBINFO_FLAG_DEFAULT;
>> info->fbops = &tegra_fb_ops;
>>
>> - err = fb_alloc_cmap(&info->cmap, 256, 0);
>> - if (err < 0) {
>> - dev_err(drm->dev, "failed to allocate color map: %d\n", err);
>> - goto destroy;
>> - }
>> -
>> drm_fb_helper_fill_fix(info, fb->pitches[0], fb->depth);
>> drm_fb_helper_fill_var(info, helper, fb->width, fb->height);
>>
>> @@ -282,7 +275,9 @@ destroy:
>> drm_framebuffer_unregister_private(fb);
>> tegra_fb_destroy(fb);
>> release:
>> - framebuffer_release(info);
>> + drm_fb_helper_release_fbi(helper);
>> +gem_unref:
>> + drm_gem_object_unreference_unlocked(&bo->gem);
>
> You can't do this. tegra_fb_alloc() takes ownership of the buffer, so
> unless you compensate for that (by taking an explicit reference to the
> buffer in tegra_fb_alloc()) you'd be dereferencing twice and likely end
> up with use-after-free errors later on.
>
> I'd prefer to keep the error clean up as it is.
Okay. I missed out on the fact that tegra_fb_destroy in the clean up
code calls drm_gem_object_unreference_unlocked. I'll keep it as is.
Archit
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
