Fix concurrency problem between dl_open and dl_iterate_phdr

3 files changed, 50 insertions, 43 deletions

diff --git a/elf/dl-load.c b/elf/dl-load.c
index aa8738f..4c14f08 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -798,22 +798,7 @@ lose (int code, int fd, const char *name, char *realname, struct link_map *l,
   /* The file might already be closed.  */
   if (fd != -1)
     (void) __close (fd);
-  if (l != NULL)
-    {
-      /* We modify the list of loaded objects.  */
-      __rtld_lock_lock_recursive (GL(dl_load_write_lock));
-      /* Remove the stillborn object from the list and free it.  */
-      assert (l->l_next == NULL);
-      if (l->l_prev == NULL)
-	/* No other module loaded. This happens only in the static library,
-	   or in rtld under --verify.  */
-	GL(dl_ns)[l->l_ns]._ns_loaded = NULL;
-      else
-	l->l_prev->l_next = NULL;
-      --GL(dl_ns)[l->l_ns]._ns_nloaded;
-      free (l);
-      __rtld_lock_unlock_recursive (GL(dl_load_write_lock));
-    }
+  free (l);
   free (realname);
 
   if (r != NULL)
@@ -898,6 +883,9 @@ _dl_map_object_from_fd (const char *name, int fd, struct filebuf *fbp,
 	 never be unloaded.  */
       __close (fd);
 
+      /* Add the map for the mirrored object to the object list.  */
+      _dl_add_to_namespace_list (l, nsid);
+
       return l;
     }
 #endif
@@ -1492,6 +1480,9 @@ cannot enable executable stack as shared object requires");
     add_name_to_object (l, ((const char *) D_PTR (l, l_info[DT_STRTAB])
 			    + l->l_info[DT_SONAME]->d_un.d_val));
 
+  /* Now that the object is fully initialized add it to the object list.  */
+  _dl_add_to_namespace_list (l, nsid);
+
 #ifdef SHARED
   /* Auditing checkpoint: we have a new object.  */
   if (__builtin_expect (GLRO(dl_naudit) > 0, 0)
@@ -2216,7 +2207,7 @@ _dl_map_object (struct link_map *loader, const char *name,
 	     have.  */
 	  static const Elf_Symndx dummy_bucket = STN_UNDEF;
 
-	  /* Enter the new object in the list of loaded objects.  */
+	  /* Allocate a new object map.  */
 	  if ((name_copy = local_strdup (name)) == NULL
 	      || (l = _dl_new_object (name_copy, name, type, loader,
 				      mode, nsid)) == NULL)
@@ -2234,6 +2225,9 @@ _dl_map_object (struct link_map *loader, const char *name,
 	  l->l_nbuckets = 1;
 	  l->l_relocated = 1;
 
+	  /* Enter the object in the object list.  */
+	  _dl_add_to_namespace_list (l, nsid);
+
 	  return l;
 	}
       else if (found_other_class)
diff --git a/elf/dl-object.c b/elf/dl-object.c
index 22a1635..5d15ce1 100644
--- a/elf/dl-object.c
+++ b/elf/dl-object.c
@@ -1,5 +1,5 @@
 /* Storage management for the chain of loaded shared objects.
-   Copyright (C) 1995-2002,2004,2006-2008,2009 Free Software Foundation, Inc.
+   Copyright (C) 1995-2002,2004,2006-2009,2010 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -26,16 +26,41 @@
 #include <assert.h>
 
 
+/* Add the new link_map NEW to the end of the namespace list.  */
+void
+internal_function
+_dl_add_to_namespace_list (struct link_map *new, Lmid_t nsid)
+{
+  /* We modify the list of loaded objects.  */
+  __rtld_lock_lock_recursive (GL(dl_load_write_lock));
+
+  if (GL(dl_ns)[nsid]._ns_loaded != NULL)
+    {
+      struct link_map *l = GL(dl_ns)[nsid]._ns_loaded;
+      while (l->l_next != NULL)
+	l = l->l_next;
+      new->l_prev = l;
+      /* new->l_next = NULL;   Would be necessary but we use calloc.  */
+      l->l_next = new;
+    }
+  else
+    GL(dl_ns)[nsid]._ns_loaded = new;
+  ++GL(dl_ns)[nsid]._ns_nloaded;
+  new->l_serial = GL(dl_load_adds);
+  ++GL(dl_load_adds);
+
+  __rtld_lock_unlock_recursive (GL(dl_load_write_lock));
+}
+
+
 /* Allocate a `struct link_map' for a new object being loaded,
    and enter it into the _dl_loaded list.  */
-
 struct link_map *
 internal_function
 _dl_new_object (char *realname, const char *libname, int type,
 		struct link_map *loader, int mode, Lmid_t nsid)
 {
   struct link_map *l;
-  int idx;
   size_t libname_len = strlen (libname) + 1;
   struct link_map *new;
   struct libname_list *newname;
@@ -93,31 +118,12 @@ _dl_new_object (char *realname, const char *libname, int type,
   new->l_scope = new->l_scope_mem;
   new->l_scope_max = sizeof (new->l_scope_mem) / sizeof (new->l_scope_mem[0]);
 
-  /* We modify the list of loaded objects.  */
-  __rtld_lock_lock_recursive (GL(dl_load_write_lock));
-
   /* Counter for the scopes we have to handle.  */
-  idx = 0;
+  int idx = 0;
 
   if (GL(dl_ns)[nsid]._ns_loaded != NULL)
-    {
-      l = GL(dl_ns)[nsid]._ns_loaded;
-      while (l->l_next != NULL)
-	l = l->l_next;
-      new->l_prev = l;
-      /* new->l_next = NULL;	Would be necessary but we use calloc.  */
-      l->l_next = new;
-
-      /* Add the global scope.  */
-      new->l_scope[idx++] = &GL(dl_ns)[nsid]._ns_loaded->l_searchlist;
-    }
-  else
-    GL(dl_ns)[nsid]._ns_loaded = new;
-  ++GL(dl_ns)[nsid]._ns_nloaded;
-  new->l_serial = GL(dl_load_adds);
-  ++GL(dl_load_adds);
-
-  __rtld_lock_unlock_recursive (GL(dl_load_write_lock));
+    /* Add the global scope.  */
+    new->l_scope[idx++] = &GL(dl_ns)[nsid]._ns_loaded->l_searchlist;
 
   /* If we have no loader the new object acts as it.  */
   if (loader == NULL)
diff --git a/elf/rtld.c b/elf/rtld.c
index 06b534a..23b3462 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -1113,6 +1113,10 @@ of this helper program; chances are you did not intend to run this program.\n\
       main_map->l_phnum = phnum;
       main_map->l_entry = *user_entry;
 
+      /* Even though the link map is not yet fully initialized we can add
+	 it to the map list since there are no possible users running yet.  */
+      _dl_add_to_namespace_list (main_map, LM_ID_BASE);
+
       /* At this point we are in a bit of trouble.  We would have to
 	 fill in the values for l_dev and l_ino.  But in general we
 	 do not know where the file is.  We also do not handle AT_EXECFD
@@ -1255,7 +1259,7 @@ of this helper program; chances are you did not intend to run this program.\n\
       /* We were invoked directly, so the program might not have a
 	 PT_INTERP.  */
       _dl_rtld_libname.name = GL(dl_rtld_map).l_name;
-      /* _dl_rtld_libname.next = NULL; 	Already zero.  */
+      /* _dl_rtld_libname.next = NULL;	Already zero.  */
       GL(dl_rtld_map).l_libname =  &_dl_rtld_libname;
     }
   else
@@ -1380,6 +1384,9 @@ of this helper program; chances are you did not intend to run this program.\n\
 	      l->l_libname->name = memcpy (copy, dsoname, len);
 	    }
 
+	  /* Add the vDSO to the object list.  */
+	  _dl_add_to_namespace_list (l, LM_ID_BASE);
+
 	  /* Rearrange the list so this DSO appears after rtld_map.  */
 	  assert (l->l_next == NULL);
 	  assert (l->l_prev == main_map);