alloc-util: add strdupa_safe() + strndupa_safe() and use it everywhere

Let's define two helpers strdupa_safe() + strndupa_safe() which do the
same as their non-safe counterparts, except that they abort if called
with allocations larger than ALLOCA_MAX.

This should ensure that all our alloca() based allocations are subject
to this limit.

afaics glibc offers three alloca() based APIs: alloca() itself,
strndupa() + strdupa(). With this we have now replacements for all of
them, that take the limit into account.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/shared/dns-domain.c b/src/shared/dns-domain.c
index 787bb8fec9..f54b187a1b 100644
--- a/src/shared/dns-domain.c
+++ b/src/shared/dns-domain.c
@@ -680,7 +680,7 @@ int dns_name_change_suffix(const char *name, const char *old_suffix, const char
         }
 
         /* Found it! Now generate the new name */
-        prefix = strndupa(name, saved_before - name);
+        prefix = strndupa_safe(name, saved_before - name);
 
         r = dns_name_concat(prefix, new_suffix, 0, ret);
         if (r < 0)
@@ -1028,7 +1028,7 @@ static bool dns_service_name_label_is_valid(const char *label, size_t n) {
         if (memchr(label, 0, n))
                 return false;
 
-        s = strndupa(label, n);
+        s = strndupa_safe(label, n);
         return dns_service_name_is_valid(s);
 }