Fix crash when system has no ipv6 address [BZ #17125]

Here's an updated patch to fix the crash in bug-ga2 when the system
has no configured ipv6 address.  I have taken a different approach of
using libc_freeres_fn instead of the libc_freeres_ptr since the former
gives better control over what is freed; we need that since cache may
or may not be allocated using malloc.

Verified that bug-ga2 works correctly in both cases and does not have
memory leaks in either of them.

1 files changed, 7 insertions, 1 deletions

diff --git a/sysdeps/unix/sysv/linux/check_pf.c b/sysdeps/unix/sysv/linux/check_pf.c
index 1bc1def72f..c7fd9b0376 100644
--- a/sysdeps/unix/sysv/linux/check_pf.c
+++ b/sysdeps/unix/sysv/linux/check_pf.c
@@ -61,7 +61,7 @@ static struct cached_data noai6ai_cached =
     .in6ailen = 0
   };
 
-libc_freeres_ptr (static struct cached_data *cache);
+static struct cached_data *cache;
 __libc_lock_define_initialized (static, lock);
 
 
@@ -401,6 +401,12 @@ __check_pf (bool *seen_ipv4, bool *seen_ipv6,
   *seen_ipv6 = true;
 }
 
+/* Free the cache if it has been allocated.  */
+libc_freeres_fn (freecache)
+{
+  if (cache)
+    __free_in6ai (cache->in6ai);
+}
 
 void
 __free_in6ai (struct in6addrinfo *ai)