nss: introduce signed integer overflow check in malloc

[Arjun Shankar]

Hi Marcus,

Thanks for the patch. The fix itself looks good to me.

There are some issues with the commit title and message. Here's a review:

> Subject: [PATCH] nss: introduce signed integer overflow check in malloc

The arguments are unsigned, and "in malloc" might give the impression
that something is fixed *within* malloc. We could also use a bug
number in the commit title. I suggest something like this instead for
the commit title:

"nss: Use reallocarray to prevent integer overflow in getaddrinfo  (bug 33977)"

Then, for the commit body,

> This concerns https://sourceware.org/bugzilla/show_bug.cgi?id=33977
> replacing realloc by realloc array introduces a basic overflow check.
> (old + count) might still overflow, but since the backend is trusted, we do not consider this to be a valid case.

1. We can drop the bug URL since we already referred to the bug number
in the commit title,
2. reallocarray should be one word without a space,
3. Suggest "NSS backend" instead of "backend"
4. Break any long lines after edits, the last line of the commit
message is a bit long

Looking forward to a v2!

Cheers

> ---
>  nss/getaddrinfo.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/nss/getaddrinfo.c b/nss/getaddrinfo.c
> index 4f6ac3358a..78f5bababc 100644
> --- a/nss/getaddrinfo.c
> +++ b/nss/getaddrinfo.c
> @@ -234,7 +234,7 @@ convert_hostent_to_gaih_addrtuple (const struct addrinfo *req, int family,
>        array = array->next;
>      }
>
> -  array = realloc (res->at, (old + count) * sizeof (*array));
> +  array = reallocarray (res->at, (old + count), sizeof (*array));

OK. reallocarray looks for a multiplication overflow and fails if there's one.

>
>    if (array == NULL)
>      return false;
> --
> 2.47.3
>

-- 
Arjun Shankar
he/him/his