Re: [patch 2/2] fbcmap: integer overflow bug

[Geert Uytterhoeven]

On Mon, Nov 15, 2010 at 05:48, Paul Mundt <lethal@xxxxxxxxxxxx> wrote:
> 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)
>> Â Â Â int rc, size = cmap->len * sizeof(u16);
>> Â Â Â struct fb_cmap umap;
>>
>> + Â Â if (cmap->len * 2 > INT_MAX)

Isn't that another integer overflow? I.e. should be "if (cmap->len >
INT_MAX / sizeof(u16))" instead?

>> + Â Â Â Â Â Â return -EINVAL;
>> +
>> Â Â Â memset(&umap, 0, sizeof(struct fb_cmap));
>> - Â Â rc = fb_alloc_cmap(&umap, cmap->len, cmap->transp != NULL);
>> + Â Â rc = fb_alloc_cmap_gfp(&umap, cmap->len, cmap->transp != NULL,
>> + Â Â Â Â Â Â Â Â Â Â Â Â Â Â GFP_KERNEL);
>> Â Â Â if (rc)
>> Â Â Â Â Â Â Â return rc;
>> Â Â Â 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.

Gr{oetje,eeting}s,

            Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
             Â Â -- Linus Torvalds
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