[BZ #1346]

2005-09-20  Roland McGrath  <roland@redhat.com>
	[BZ #1346]
	* elf/dl-load.c (_dl_map_object_from_fd) [HAVE_Z_RELRO]: Do relro
	magic on __stack_prot only if [SHARED].  Skip mprotect if __stack_prot
	lies outside the page-rounded-down relro region.

1 files changed, 23 insertions, 9 deletions

diff --git a/elf/dl-load.c b/elf/dl-load.c
index 58b0f91731..9a780beae8 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -1354,22 +1354,36 @@ cannot allocate TLS data structures for initial thread");
 
   if (__builtin_expect ((stack_flags &~ GL(dl_stack_flags)) & PF_X, 0))
     {
+      if (__builtin_expect (__check_caller (RETURN_ADDRESS (0), allow_ldso),
+			    0) != 0)
+	{
+	  errstring = N_("invalid caller");
+	  goto call_lose;
+	}
+
       /* The stack is presently not executable, but this module
 	 requires that it be executable.  We must change the
 	 protection of the variable which contains the flags used in
 	 the mprotect calls.  */
-#ifdef HAVE_Z_RELRO
+#if defined HAVE_Z_RELRO && defined SHARED
       if ((mode & (__RTLD_DLOPEN | __RTLD_AUDIT)) == __RTLD_DLOPEN)
 	{
-	  uintptr_t p = ((uintptr_t) &__stack_prot) & ~(GLRO(dl_pagesize) - 1);
-	  size_t s = (uintptr_t) &__stack_prot - p + sizeof (int);
-
-	  __mprotect ((void *) p, s, PROT_READ|PROT_WRITE);
-	  if (__builtin_expect (__check_caller (RETURN_ADDRESS (0),
-						allow_ldso) == 0,
-				0))
+	  const uintptr_t p = (uintptr_t) &__stack_prot & -GLRO(dl_pagesize);
+	  const size_t s = (uintptr_t) (&__stack_prot + 1) - p;
+
+	  struct link_map *const m = &GL(dl_rtld_map);
+	  const uintptr_t relro_end = ((m->l_addr + m->l_relro_addr
+					+ m->l_relro_size)
+				       & -GLRO(dl_pagesize));
+	  if (__builtin_expect (p + s <= relro_end, 1))
+	    {
+	      /* The variable lies in the region protected by RELRO.  */
+	      __mprotect ((void *) p, s, PROT_READ|PROT_WRITE);
+	      __stack_prot |= PROT_READ|PROT_WRITE|PROT_EXEC;
+	      __mprotect ((void *) p, s, PROT_READ);
+	    }
+	  else
 	    __stack_prot |= PROT_READ|PROT_WRITE|PROT_EXEC;
-	  __mprotect ((void *) p, s, PROT_READ);
 	}
       else
 #endif