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[PATCH] nss_db: Fix initialization of iteration position [BZ #20237]

When get*ent is called without a preceding set*ent, we need
to set the initial iteration position in get*ent.

Reproducer: Add âservices: db filesâ to /etc/nsswitch.conf, then run
âperl -e getserventâ.  It will segfault before this change, and exit
silently after it.

2016-06-10  Florian Weimer  <>

	[BZ #20237]
	* nss/nss_db/db-XXX.c (set*ent): Reset entidx to NULL.
	(get*ent): Set entidx to NULL during initialization.  If entidx is
	NULL, start iteration from the beginning.

diff --git a/nss/nss_db/db-XXX.c b/nss/nss_db/db-XXX.c
index 125a5e9..2d13edd 100644
--- a/nss/nss_db/db-XXX.c
+++ b/nss/nss_db/db-XXX.c
@@ -77,7 +77,7 @@ CONCAT(_nss_db_set,ENTNAME) (int stayopen)
       keep_db |= stayopen;
       /* Reset the sequential index.  */
-      entidx  = (const char *) state.header + state.header->valstroffset;
+      entidx  = NULL;
   __libc_lock_unlock (lock);
@@ -253,8 +253,14 @@ CONCAT(_nss_db_get,ENTNAME_r) (struct STRUCTURE *result, char *buffer,
 	  goto out;
+      entidx = NULL;
+  /* Start from the beginning if freshly initialized or reset
+     requested by set*ent.  */
+  if (entidx == NULL)
+    entidx = (const char *) state.header + state.header->valstroffset;
   if (state.header != MAP_FAILED)

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