[PATCH v4.] nss: Use reallocarray to prevent integer overflow in getaddrinfo (bug 33977)

replacing realloc by reallocarray introduces a basic overflow check.
(old + count) might still overflow, but since the NSS backend is trusted,
we do not consider this to be a valid case.
---
v1: https://inbox.sourceware.org/libc-alpha/[email protected]/
v2: iterated on Arjuns and Andreas review comments
v3: re-submission to support existing tooling
v4: moved from reallocarray to __libc_reallocarray due to a regression found by Adhemerval
---
 nss/getaddrinfo.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/nss/getaddrinfo.c b/nss/getaddrinfo.c
index 4f6ac3358a..45b7f728a1 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 = __libc_reallocarray (res->at, old + count, sizeof (*array));
 
   if (array == NULL)
     return false;
-- 
2.47.3