Re: [PATCH v2] fbdev: platinumfb: add error checking for ioremap calls

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Unchecked request_mem_region combined with unconditional release_mem_region causes resource corruption and Use-After-Free.
--

--- Patch [1]: [PATCH v2] fbdev: platinumfb: add error checking for ioremap calls ---
commit a9dd2a2a25aeae119ea17d0f40c6cbdddde67dfd
Author: yuebingkun <[email protected]>

fbdev: platinumfb: add error checking for ioremap calls
    
This commit adds error checking for ioremap() and ioremap_wt() calls in
platinumfb_probe(), avoiding NULL pointer dereferences by introducing
goto-based cleanup paths on failure.

> diff --git a/drivers/video/fbdev/platinumfb.c b/drivers/video/fbdev/platinumfb.c
> index a08d955d9b439..f74c937c839f8 100644
> --- a/drivers/video/fbdev/platinumfb.c
> +++ b/drivers/video/fbdev/platinumfb.c
[ ... ]
> @@ -567,15 +567,30 @@ static int platinumfb_probe(struct platform_device* odev)
[ ... ]
>  	pinfo->cmap_regs_phys = 0xf301b000;	/* XXX not in prom? */
>  	request_mem_region(pinfo->cmap_regs_phys, 0x1000, "platinumfb cmap");
>  	pinfo->cmap_regs = ioremap(pinfo->cmap_regs_phys, 0x1000);
> +	if (!pinfo->cmap_regs) {
> +		dev_err(&odev->dev, "failed to ioremap cmap registers\n");
> +		rc = -ENOMEM;
> +		goto err_release_cmap;
> +	}
[ ... ]
> +err_unmap_cmap:
> +	iounmap(pinfo->cmap_regs);
> +err_release_cmap:
> +	release_mem_region(pinfo->cmap_regs_phys, 0x1000);

[Severity: High]
This is a pre-existing issue, but I noticed the return value of
request_mem_region() is ignored just before the ioremap() call.

If request_mem_region() fails because the physical resource is already
claimed by platform code or another driver, probe continues. If a subsequent
step then fails, such as ioremap() returning NULL or platinum_init_fb()
failing, this newly added error path branches to err_release_cmap.

Since err_release_cmap unconditionally calls release_mem_region(), does this
risk freeing a resource that wasn't actually acquired? If the region size
and start address exactly match an existing claim, this could unlink and
free a resource owned by another driver, potentially causing a
use-after-free later.

Could we add a check for the return value of request_mem_region() so we
only release it if the driver successfully claimed it?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=1