[patch] ngx_http_image_filter_module incorrectly calculates size

[Maxim Bublis]

Hi.

>> I think it should be correct solution if multiplication of either dx
>> and ctx->max_height or dy and ctx->max_width would not result in
>> integer overflow in case when both dx and ctx->max_height or dy and
>> ctx->max_height are rather large integers.
>
> While real-world image sizes shouldn't be the problem (and if they
> will, we'll notice this in other places as these multiplications
> are done anyway), but I missed the special case of '-' in config,
> which will result in max_width / max_height being set to maximum
> possible value.
>
> The following patch should be better:
>
> --- a/src/http/modules/ngx_http_image_filter_module.c
> +++ b/src/http/modules/ngx_http_image_filter_module.c
> @@ -817,9 +817,7 @@ transparent:
>
>         resize = 0;
>
> -        if ((ngx_uint_t) (dx * 100 / dy)
> -            < ctx->max_width * 100 / ctx->max_height)
> -        {
> +        if ((double) dx / dy < (double) ctx->max_width / ctx->max_height) {
>             if ((ngx_uint_t) dx > ctx->max_width) {
>                 dy = dy * ctx->max_width / dx;
>                 dy = dy ? dy : 1;


It seems like everything is fine now. Should it be expected that
bugfix to be applied upstream?


-- 
Maxim Bublis