linux-kernel - Re: [patch 2/2] fbcmap: integer overflow bug

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Date:	Mon, 15 Nov 2010 13:48:20 +0900
From:	Paul Mundt <lethal@...ux-sh.org>
To:	Dan Carpenter <error27@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [patch 2/2] fbcmap: integer overflow bug

On Sat, Nov 13, 2010 at 01:07:18PM +0300, Dan Carpenter wrote:
> @@ -256,8 +264,12 @@ int fb_set_user_cmap(struct fb_cmap_user *cmap, struct fb_info *info)
>  	int rc, size = cmap->len * sizeof(u16);
>  	struct fb_cmap umap;
>  
> +	if (cmap->len * 2 > INT_MAX)
> +		return -EINVAL;
> +
>  	memset(&umap, 0, sizeof(struct fb_cmap));
> -	rc = fb_alloc_cmap(&umap, cmap->len, cmap->transp != NULL);
> +	rc = fb_alloc_cmap_gfp(&umap, cmap->len, cmap->transp != NULL,
> +				GFP_KERNEL);
>  	if (rc)
>  		return rc;
>  	if (copy_from_user(umap.red, cmap->red, size) ||

This looks reasonable, but it probably makes more sense to use -E2BIG
for the overflow case (as other cases are doing already), and also just
to check size directly rather than open-coding the * 2.
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