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, 37 insertions, 0 deletions

diff --git a/elf/tst-nodelete2.c b/elf/tst-nodelete2.c
new file mode 100644
index 0000000000..388e8afb32
--- /dev/null
+++ b/elf/tst-nodelete2.c
@@ -0,0 +1,37 @@
+#include "../dlfcn/dlfcn.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <gnu/lib-names.h>
+
+static int
+do_test (void)
+{
+  int result = 0;
+
+  printf ("\nOpening pthread library.\n");
+  void *pthread = dlopen (LIBPTHREAD_SO, RTLD_LAZY);
+
+  /* This is a test for correct DF_1_NODELETE clearing when dlopen failure
+     happens.  We should clear DF_1_NODELETE for failed library only, because
+     doing this for others (e.g. libpthread) might cause them to be unloaded,
+     that may lead to some global references (e.g. __rtld_lock_unlock) to be
+     broken.  The dlopen should fail because of undefined symbols in shared
+     library, that cause DF_1_NODELETE to be cleared.  For libpthread, this
+     flag should be set, because if not, SIGSEGV will happen in dlclose.  */
+  if (dlopen ("tst-nodelete2mod.so", RTLD_NOW) != NULL)
+    {
+      printf ("Unique symbols test failed\n");
+      result = 1;
+    }
+
+  if (pthread)
+    dlclose (pthread);
+
+  if (result == 0)
+    printf ("SUCCESS\n");
+
+  return result;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"