[glibc] gaiconf_init: Avoid double-free in label and precedence lists

[Siddhesh Poyarekar <siddhesh@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=77a34079d8f3d63b61543bf3af93043f8674e4c4

commit 77a34079d8f3d63b61543bf3af93043f8674e4c4
Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date:   Tue Aug 3 21:11:03 2021 +0530

    gaiconf_init: Avoid double-free in label and precedence lists
    
    labellist and precedencelist could get freed a second time if there
    are allocation failures, so set them to NULL to avoid a double-free.
    
    Reviewed-by: Arjun Shankar <arjun@redhat.com>

Diff:
---
 sysdeps/posix/getaddrinfo.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sysdeps/posix/getaddrinfo.c b/sysdeps/posix/getaddrinfo.c
index 838a68f022..43dfc6739e 100644
--- a/sysdeps/posix/getaddrinfo.c
+++ b/sysdeps/posix/getaddrinfo.c
@@ -2008,6 +2008,7 @@ gaiconf_init (void)
 	      l = l->next;
 	    }
 	  free_prefixlist (labellist);
+	  labellist = NULL;
 
 	  /* Sort the entries so that the most specific ones are at
 	     the beginning.  */
@@ -2046,6 +2047,7 @@ gaiconf_init (void)
 	      l = l->next;
 	    }
 	  free_prefixlist (precedencelist);
+	  precedencelist = NULL;
 
 	  /* Sort the entries so that the most specific ones are at
 	     the beginning.  */