commit 99135114ba23c3110b7e4e650fabdc5e639746b7

Author: DJ Delorie <dj@redhat.com>

Date:   Fri Jun 28 18:30:00 2019 -0500

    nss_db: fix endent wrt NULL mappings [BZ #24695] [BZ #24696]

    nss_db allows for getpwent et al to be called without a set*ent,

    but it only works once.  After the last get*ent a set*ent is

    required to restart, because the end*ent did not properly reset

    the module.  Resetting it to NULL allows for a proper restart.

    If the database doesn't exist, however, end*ent erroniously called

    munmap which set errno.

Note: the test case has not been included in this backport as the

required test harness infrastructure does not exist.

diff --git a/nss/nss_db/db-open.c b/nss/nss_db/db-open.c

index 8a83d6b..3fa11e9 100644

--- a/nss/nss_db/db-open.c

+++ b/nss/nss_db/db-open.c

@@ -63,5 +63,9 @@ internal_setent (const char *file, struct nss_db_map *mapping)

 void

 internal_endent (struct nss_db_map *mapping)

 {

-  munmap (mapping->header, mapping->len);

+  if (mapping->header != NULL)

+    {

+      munmap (mapping->header, mapping->len);

+      mapping->header = NULL;

+    }

 }