Clear DF_1_NODELETE flag only for failed to load library.

https://sourceware.org/bugzilla/show_bug.cgi?id=18778

If dlopen fails to load an object that has triggered loading libpthread it
causes ld.so to unload libpthread because its DF_1_NODELETE flags has been
forcefully cleared. The next call to __rtdl_unlock_lock_recursive will crash
since pthread_mutex_unlock no longer exists.

This patch moves l->l_flags_1 &= ~DF_1_NODELETE out of loop through all loaded
libraries and performs the action only on inconsistent one.

	[BZ #18778]
	* elf/Makefile (tests): Add Add tst-nodelete2.
	(modules-names): Add tst-nodelete2mod.
	(tst-nodelete2mod.so-no-z-defs): New.
	($(objpfx)tst-nodelete2): Likewise.
	($(objpfx)tst-nodelete2.out): Likewise.
	(LDFLAGS-tst-nodelete2): Likewise.
	* elf/dl-close.c (_dl_close_worker): Move DF_1_NODELETE clearing
	out of loop through all loaded libraries.
	* elf/tst-nodelete2.c: New file.
	* elf/tst-nodelete2mod.c: Likewise.

1 files changed, 7 insertions, 0 deletions

diff --git a/elf/tst-nodelete2mod.c b/elf/tst-nodelete2mod.c
new file mode 100644
index 0000000000..e88c756f5e
--- /dev/null
+++ b/elf/tst-nodelete2mod.c
@@ -0,0 +1,7 @@
+/* Undefined symbol.  */
+extern int not_exist (void);
+
+int foo (void)
+{
+  return not_exist ();
+}