Re: [PATCH v2 5/6] drm/msm: fbdev: Use a DRM client buffer

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Unbalanced `vmap_count` decrement and kernel warning on probe error path.
--

commit a68322c2e5e8736f3b039ddfe130065a05ddf719
Author: Thomas Zimmermann <tzimmermann@suse.de>
drm/msm: fbdev: Use a DRM client buffer

This commit replaces the internal DRM framebuffer with a DRM client buffer
in msm_fbdev. It unifies framebuffer allocation for DRM clients in user
space and the internal fbdev emulation, and simplifies the clean-up side.

> diff --git a/drivers/gpu/drm/msm/msm_fbdev.c b/drivers/gpu/drm/msm/msm_fbdev.c
> index 5532c5779f17c..f14db46aa51e2 100644
> --- a/drivers/gpu/drm/msm/msm_fbdev.c
> +++ b/drivers/gpu/drm/msm/msm_fbdev.c

[ ... ]

> @@ -162,19 +161,29 @@ int msm_fbdev_driver_fbdev_probe(struct drm_fb_helper *helper,
>  	fbi->screen_buffer = msm_gem_get_vaddr(bo);
>  	if (IS_ERR(fbi->screen_buffer)) {
>  		ret = PTR_ERR(fbi->screen_buffer);
> -		goto err_drm_framebuffer_remove;
> +		goto err_msm_gem_put_vaddr;

[Severity: Medium]
If msm_gem_get_vaddr() fails and returns an error pointer, the vmap_count
is not incremented. Does jumping to err_msm_gem_put_vaddr here cause an
unbalanced msm_gem_put_vaddr() call that will underflow vmap_count and
trigger a GEM_WARN_ON() kernel warning?

It seems this should instead skip the put_vaddr step and jump straight to
err_drm_client_buffer_delete.

>  	}
>  	fbi->screen_size = bo->size;
>  	fbi->fix.smem_start = paddr;
>  	fbi->fix.smem_len = bo->size;

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260618141249.151338-1-tzimmermann@suse.de?part=5