Add forced deletion support to _dl_close_worker

https://sourceware.org/bugzilla/show_bug.cgi?id=17833

I've a shared library that contains both undefined and unique symbols.
Then I try to call the following sequence of dlopen:

1. dlopen("./libfoo.so", RTLD_NOW)
2. dlopen("./libfoo.so", RTLD_LAZY | RTLD_GLOBAL)

First dlopen call terminates with error because of undefined symbols,
but STB_GNU_UNIQUE ones set DF_1_NODELETE flag and hence block library
in the memory.

The library goes into inconsistent state as several structures remain
uninitialized. For instance, relocations for GOT table were not performed.

By the time of second dlopen call this library looks like as it would be
fully initialized but this is not true: any call through incorrect GOT
table leads to segmentation fault.  On some systems this inconsistency
triggers assertions in the dynamic linker.

This patch adds a parameter to _dl_close_worker to implement forced object
deletion in case of dlopen() failure:

1. Clears DF_1_NODELETE bit if forced, to allow library to be removed from
memory.
2. For each unique symbol that is defined in this object clears
appropriate entry in _ns_unique_sym_table.

	[BZ #17833]
	* elf/Makefile (tests): Add tst-nodelete.
	(modules-names): Add tst-nodelete-uniquemod.
	(tst-nodelete-uniquemod.so-no-z-defs): New.
	(tst-nodelete-rtldmod.so-no-z-defs): Likewise.
	(tst-nodelete-zmod.so-no-z-defs): Likewise.
	($(objpfx)tst-nodelete): Likewise.
	($(objpfx)tst-nodelete.out): Likewise.
	(LDFLAGS-tst-nodelete): Likewise.
	(LDFLAGS-tst-nodelete-zmod.so): Likewise.
	* elf/dl-close.c (_dl_close_worker): Add a parameter to
	implement forced object deletion.
	(_dl_close): Pass false to _dl_close_worker.
	* elf/dl-open.c (_dl_open): Pass true to _dl_close_worker.
	* elf/tst-nodelete.cc: New file.
	* elf/tst-nodeletelib.cc: Likewise.
	* elf/tst-znodeletelib.cc: Likewise.
	* include/dlfcn.h (_dl_close_worker): Add a new parameter.

8 files changed, 130 insertions, 5 deletions

diff --git a/elf/Makefile b/elf/Makefile
index f21276c006..bd0f24dd51 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -132,7 +132,7 @@ tests += $(tests-static)
 ifeq (yes,$(build-shared))
 tests += loadtest restest1 preloadtest loadfail multiload origtest resolvfail \
 	 constload1 order noload filter unload \
-	 reldep reldep2 reldep3 reldep4 nodelete nodelete2 \
+	 reldep reldep2 reldep3 reldep4 nodelete nodelete2 tst-nodelete \
 	 nodlopen nodlopen2 neededtest neededtest2 \
 	 neededtest3 neededtest4 unload2 lateglobal initfirst global \
 	 restest2 next dblload dblunload reldep5 reldep6 reldep7 reldep8 \
@@ -207,7 +207,9 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
 		tst-unique1mod1 tst-unique1mod2 \
 		tst-unique2mod1 tst-unique2mod2 \
 		tst-auditmod9a tst-auditmod9b \
-		$(if $(CXX),tst-unique3lib tst-unique3lib2 tst-unique4lib) \
+		$(if $(CXX),tst-unique3lib tst-unique3lib2 tst-unique4lib \
+		  tst-nodelete-uniquemod) \
+		tst-nodelete-rtldmod tst-nodelete-zmod \
 		tst-initordera1 tst-initorderb1 \
 		tst-initordera2 tst-initorderb2 \
 		tst-initordera3 tst-initordera4 \
@@ -591,6 +593,9 @@ ifuncmod5.so-no-z-defs = yes
 ifuncmod6.so-no-z-defs = yes
 tst-auditmod9a.so-no-z-defs = yes
 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
 
 ifeq ($(build-shared),yes)
 # Build all the modules even when not actually running test programs.
@@ -1153,6 +1158,14 @@ $(objpfx)tst-unique3.out: $(objpfx)tst-unique3lib2.so
 
 $(objpfx)tst-unique4: $(objpfx)tst-unique4lib.so
 
+$(objpfx)tst-nodelete: $(libdl)
+$(objpfx)tst-nodelete.out: $(objpfx)tst-nodelete-uniquemod.so \
+			   $(objpfx)tst-nodelete-rtldmod.so \
+			   $(objpfx)tst-nodelete-zmod.so
+
+LDFLAGS-tst-nodelete = -rdynamic
+LDFLAGS-tst-nodelete-zmod.so = -Wl,--enable-new-dtags,-z,nodelete
+
 $(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 412f71d70b..2104674bd0 100644
--- a/elf/dl-close.c
+++ b/elf/dl-close.c
@@ -108,7 +108,7 @@ remove_slotinfo (size_t idx, struct dtv_slotinfo_list *listp, size_t disp,
 
 
 void
-_dl_close_worker (struct link_map *map)
+_dl_close_worker (struct link_map *map, bool force)
 {
   /* One less direct use.  */
   --map->l_direct_opencount;
@@ -152,6 +152,10 @@ _dl_close_worker (struct link_map *map)
       l->l_idx = idx;
       maps[idx] = l;
       ++idx;
+
+      /* Clear DF_1_NODELETE to force object deletion.  */
+      if (force)
+	l->l_flags_1 &= ~DF_1_NODELETE;
     }
   assert (idx == nloaded);
 
@@ -635,6 +639,31 @@ _dl_close_worker (struct link_map *map)
 		}
 	    }
 
+	  /* Reset unique symbols if forced.  */
+	  if (force)
+	    {
+	      struct unique_sym_table *tab = &ns->_ns_unique_sym_table;
+	      __rtld_lock_lock_recursive (tab->lock);
+	      struct unique_sym *entries = tab->entries;
+	      if (entries != NULL)
+		{
+		  size_t idx, size = tab->size;
+		  for (idx = 0; idx < size; ++idx)
+		    {
+		      /* Clear unique symbol entries that belong to this
+			 object.  */
+		      if (entries[idx].name != NULL
+			  && entries[idx].map == imap)
+			{
+			  entries[idx].name = NULL;
+			  entries[idx].hashval = 0;
+			  tab->n_elements--;
+			}
+		    }
+		}
+	      __rtld_lock_unlock_recursive (tab->lock);
+	    }
+
 	  /* We can unmap all the maps at once.  We determined the
 	     start address and length when we loaded the object and
 	     the `munmap' call does the rest.  */
@@ -782,7 +811,7 @@ _dl_close (void *_map)
   /* Acquire the lock.  */
   __rtld_lock_lock_recursive (GL(dl_load_lock));
 
-  _dl_close_worker (map);
+  _dl_close_worker (map, false);
 
   __rtld_lock_unlock_recursive (GL(dl_load_lock));
 }
diff --git a/elf/dl-open.c b/elf/dl-open.c
index 2d0e082271..027c1e0eda 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -670,7 +670,7 @@ no more namespaces available for dlmopen()"));
 	  if ((mode & __RTLD_AUDIT) == 0)
 	    GL(dl_tls_dtv_gaps) = true;
 
-	  _dl_close_worker (args.map);
+	  _dl_close_worker (args.map, true);
 	}
 
       assert (_dl_debug_initialize (0, args.nsid)->r_state == RT_CONSISTENT);
diff --git a/elf/tst-nodelete-rtldmod.cc b/elf/tst-nodelete-rtldmod.cc
new file mode 100644
index 0000000000..740e1d8181
--- /dev/null
+++ b/elf/tst-nodelete-rtldmod.cc
@@ -0,0 +1,6 @@
+extern int not_exist (void);
+
+int foo (void)
+{
+  return not_exist ();
+}
diff --git a/elf/tst-nodelete-uniquemod.cc b/elf/tst-nodelete-uniquemod.cc
new file mode 100644
index 0000000000..632b303d58
--- /dev/null
+++ b/elf/tst-nodelete-uniquemod.cc
@@ -0,0 +1,14 @@
+extern int not_exist (void);
+
+inline int make_unique (void)
+{
+  /* Static variables in inline functions and classes
+     generate STB_GNU_UNIQUE symbols.  */
+  static int unique;
+  return ++unique;
+}
+
+int foo (void)
+{
+  return make_unique () + not_exist ();
+}
diff --git a/elf/tst-nodelete-zmod.cc b/elf/tst-nodelete-zmod.cc
new file mode 100644
index 0000000000..740e1d8181
--- /dev/null
+++ b/elf/tst-nodelete-zmod.cc
@@ -0,0 +1,6 @@
+extern int not_exist (void);
+
+int foo (void)
+{
+  return not_exist ();
+}
diff --git a/elf/tst-nodelete.cc b/elf/tst-nodelete.cc
new file mode 100644
index 0000000000..176cb68836
--- /dev/null
+++ b/elf/tst-nodelete.cc
@@ -0,0 +1,51 @@
+#include "../dlfcn/dlfcn.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+static int
+do_test (void)
+{
+  int result = 0;
+
+  /* This is a test for correct handling of dlopen failures for library that
+     is loaded with RTLD_NODELETE flag.  The first dlopen should fail because
+     of undefined symbols in shared library.  The second dlopen then verifies
+     that library was properly unloaded.  */
+  if (dlopen ("tst-nodelete-rtldmod.so", RTLD_NOW | RTLD_NODELETE) != NULL
+      || dlopen ("tst-nodelete-rtldmod.so", RTLD_LAZY | RTLD_NOLOAD) != NULL)
+    {
+      printf ("RTLD_NODELETE test failed\n");
+      result = 1;
+    }
+
+  /* This is a test for correct handling of dlopen failures for library that
+     is linked with '-z nodelete' option and hence has DF_1_NODELETE flag.
+     The first dlopen should fail because of undefined symbols in shared
+     library.  The second dlopen then verifies that library was properly
+     unloaded.  */
+  if (dlopen ("tst-nodelete-zmod.so", RTLD_NOW) != NULL
+      || dlopen ("tst-nodelete-zmod.so", RTLD_LAZY | RTLD_NOLOAD) != NULL)
+    {
+      printf ("-z nodelete test failed\n");
+      result = 1;
+    }
+
+   /* This is a test for correct handling of dlopen failures for library
+     with unique symbols.  The first dlopen should fail because of undefined
+     symbols in shared library.  The second dlopen then verifies that library
+     was properly unloaded.  */
+  if (dlopen ("tst-nodelete-uniquemod.so", RTLD_NOW) != NULL
+      || dlopen ("tst-nodelete-uniquemod.so", RTLD_LAZY | RTLD_NOLOAD) != NULL)
+    {
+      printf ("Unique symbols test failed\n");
+      result = 1;
+    }
+
+  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-znodelete-zlib.cc
new file mode 100644
index 0000000000..1e8f3686d7
--- /dev/null
+++ b/elf/tst-znodelete-zlib.cc
@@ -0,0 +1,6 @@
+extern int not_exist (void);
+
+int foo (void)
+{
+  return  not_exist ();
+}