[glibc/ibm/2.32/master] nscd: Fix double free in netgroupcache [BZ #27462]

[glibc/ibm/2.32/master] nscd: Fix double free in netgroupcache [BZ #27462]

[Tulio Magno Quites Machado Filho]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=1d4526569162e6c8f0789eb077492730b0756b3b

commit 1d4526569162e6c8f0789eb077492730b0756b3b
Author: DJ Delorie <dj@redhat.com>
Date:   Thu Feb 25 16:08:21 2021 -0500

    nscd: Fix double free in netgroupcache [BZ #27462]
    
    In commit 745664bd798ec8fd50438605948eea594179fba1 a use-after-free
    was fixed, but this led to an occasional double-free.  This patch
    tracks the "live" allocation better.
    
    Tested manually by a third party.
    
    Related: RHBZ 1927877
    
    Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
    Reviewed-by: Carlos O'Donell <carlos@redhat.com>
    (cherry picked from commit dca565886b5e8bd7966e15f0ca42ee5cff686673)

Diff:
---
 nscd/netgroupcache.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/nscd/netgroupcache.c b/nscd/netgroupcache.c
index 88c69d1e9c..381aa721ef 100644
--- a/nscd/netgroupcache.c
+++ b/nscd/netgroupcache.c
@@ -248,7 +248,7 @@ addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
 					     : NULL);
 				    ndomain = (ndomain ? newbuf + ndomaindiff
 					       : NULL);
-				    buffer = newbuf;
+				    *tofreep = buffer = newbuf;
 				  }
 
 				nhost = memcpy (buffer + bufused,
@@ -319,7 +319,7 @@ addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
 		    else if (status == NSS_STATUS_TRYAGAIN && e == ERANGE)
 		      {
 			buflen *= 2;
-			buffer = xrealloc (buffer, buflen);
+			*tofreep = buffer = xrealloc (buffer, buflen);
 		      }
 		    else if (status == NSS_STATUS_RETURN
 			     || status == NSS_STATUS_NOTFOUND