[glibc] CVE-2024-33600: nscd: Do not send missing not-found response in addgetnetgrentX (bug 31678)

[Florian Weimer <fw@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=7835b00dbce53c3c87bbbb1754a95fb5e58187aa

commit 7835b00dbce53c3c87bbbb1754a95fb5e58187aa
Author: Florian Weimer <fweimer@redhat.com>
Date:   Thu Apr 25 15:01:07 2024 +0200

    CVE-2024-33600: nscd: Do not send missing not-found response in addgetnetgrentX (bug 31678)
    
    If we failed to add a not-found response to the cache, the dataset
    point can be null, resulting in a null pointer dereference.
    
    Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

Diff:
---
 nscd/netgroupcache.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/nscd/netgroupcache.c b/nscd/netgroupcache.c
index f227dc7fa2..c18fe111f3 100644
--- a/nscd/netgroupcache.c
+++ b/nscd/netgroupcache.c
@@ -147,7 +147,7 @@ addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
       /* No such service.  */
       cacheable = do_notfound (db, fd, req, key, &dataset, &total, &timeout,
 			       &key_copy);
-      goto writeout;
+      goto maybe_cache_add;
     }
 
   memset (&data, '\0', sizeof (data));
@@ -348,7 +348,7 @@ addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
     {
       cacheable = do_notfound (db, fd, req, key, &dataset, &total, &timeout,
 			       &key_copy);
-      goto writeout;
+      goto maybe_cache_add;
     }
 
   total = buffilled;
@@ -410,14 +410,12 @@ addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
   }
 
   if (he == NULL && fd != -1)
-    {
-      /* We write the dataset before inserting it to the database
-	 since while inserting this thread might block and so would
-	 unnecessarily let the receiver wait.  */
-    writeout:
+    /* We write the dataset before inserting it to the database since
+       while inserting this thread might block and so would
+       unnecessarily let the receiver wait.  */
       writeall (fd, &dataset->resp, dataset->head.recsize);
-    }
 
+ maybe_cache_add:
   if (cacheable)
     {
       /* If necessary, we also propagate the data to disk.  */