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.

4 files changed, 56 insertions, 10 deletions

diff --git a/elf/Makefile b/elf/Makefile
index 4ceeaf8..71a18a1 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -148,7 +148,8 @@ tests += loadtest restest1 preloadtest loadfail multiload origtest resolvfail \
 	 tst-unique1 tst-unique2 $(if $(CXX),tst-unique3 tst-unique4 \
 	 tst-nodelete) \
 	 tst-initorder tst-initorder2 tst-relsort1 tst-null-argv \
-	 tst-ptrguard1 tst-tlsalign tst-tlsalign-extern tst-nodelete-opened
+	 tst-ptrguard1 tst-tlsalign tst-tlsalign-extern tst-nodelete-opened \
+	 tst-nodelete2
 #	 reldep9
 ifeq ($(build-hardcoded-path-in-tests),yes)
 tests += tst-dlopen-aout
@@ -218,7 +219,7 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
 		tst-initorder2d \
 		tst-relsort1mod1 tst-relsort1mod2 tst-array2dep \
 		tst-array5dep tst-null-argv-lib \
-		tst-tlsalign-lib tst-nodelete-opened-lib
+		tst-tlsalign-lib tst-nodelete-opened-lib tst-nodelete2mod
 ifeq (yes,$(have-protected-data))
 modules-names += tst-protected1moda tst-protected1modb
 tests += tst-protected1a tst-protected1b
@@ -594,6 +595,7 @@ tst-auditmod9b.so-no-z-defs = yes
 tst-nodelete-uniquemod.so-no-z-defs = yes
 tst-nodelete-rtldmod.so-no-z-defs = yes
 tst-nodelete-zmod.so-no-z-defs = yes
+tst-nodelete2mod.so-no-z-defs = yes
 
 ifeq ($(build-shared),yes)
 # Build all the modules even when not actually running test programs.
@@ -1164,6 +1166,11 @@ $(objpfx)tst-nodelete.out: $(objpfx)tst-nodelete-uniquemod.so \
 LDFLAGS-tst-nodelete = -rdynamic
 LDFLAGS-tst-nodelete-zmod.so = -Wl,--enable-new-dtags,-z,nodelete
 
+$(objpfx)tst-nodelete2: $(libdl)
+$(objpfx)tst-nodelete2.out: $(objpfx)tst-nodelete2mod.so
+
+LDFLAGS-tst-nodelete2 = -rdynamic
+
 $(objpfx)tst-initorder-cmp.out: tst-initorder.exp $(objpfx)tst-initorder.out
 	cmp $^ > $@; \
 	$(evaluate-test)
diff --git a/elf/dl-close.c b/elf/dl-close.c
index 9105277..c897247 100644
--- a/elf/dl-close.c
+++ b/elf/dl-close.c
@@ -144,6 +144,14 @@ _dl_close_worker (struct link_map *map, bool force)
   char done[nloaded];
   struct link_map *maps[nloaded];
 
+  /* Clear DF_1_NODELETE to force object deletion.  We don't need to touch
+     l_tls_dtor_count because forced object deletion only happens when an
+     error occurs during object load.  Destructor registration for TLS
+     non-POD objects should not have happened till then for this
+     object.  */
+  if (force)
+    map->l_flags_1 &= ~DF_1_NODELETE;
+
   /* Run over the list and assign indexes to the link maps and enter
      them into the MAPS array.  */
   int idx = 0;
@@ -153,13 +161,6 @@ _dl_close_worker (struct link_map *map, bool force)
       maps[idx] = l;
       ++idx;
 
-      /* Clear DF_1_NODELETE to force object deletion.  We don't need to touch
-	 l_tls_dtor_count because forced object deletion only happens when an
-	 error occurs during object load.  Destructor registration for TLS
-	 non-POD objects should not have happened till then for this
-	 object.  */
-      if (force)
-	l->l_flags_1 &= ~DF_1_NODELETE;
     }
   assert (idx == nloaded);
 
diff --git a/elf/tst-nodelete2.c b/elf/tst-nodelete2.c
new file mode 100644
index 0000000..388e8af
--- /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"
diff --git a/elf/tst-znodelete-zlib.cc b/elf/tst-nodelete2mod.c
index 1e8f368..e88c756 100644
--- a/elf/tst-znodelete-zlib.cc
+++ b/elf/tst-nodelete2mod.c
@@ -1,6 +1,7 @@
+/* Undefined symbol.  */
 extern int not_exist (void);
 
 int foo (void)
 {
-  return  not_exist ();
+  return not_exist ();
 }