Fix illegal memory accesses in the assembler when attempting to parse corrup tinput files.

	PR 23054
	* cond.c (s_ifsef): Replace use of obstack_copy with obstack_alloc
	followed by memcpy.
	(s_if, s_ifb, s_ifc, s_ifeqs): Likewise.
	* obj-elf.c (elf_adjust_symtab): Check for local symbols before
	attempting to dereference the sy_next field of a symbol.
	* stabs.c (get_stab_string_offset): Fail if there is no string
	following the stab directive.

4 files changed, 41 insertions, 17 deletions

diff --git a/gas/ChangeLog b/gas/ChangeLog
index 874c3a2..2f478be 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,14 @@
+2018-04-16  Nick Clifton  <nickc@redhat.com>
+
+	PR 23054
+	* cond.c (s_ifsef): Replace use of obstack_copy with obstack_alloc
+	followed by memcpy.
+	(s_if, s_ifb, s_ifc, s_ifeqs): Likewise.
+	* obj-elf.c (elf_adjust_symtab): Check for local symbols before
+	attempting to dereference the sy_next field of a symbol.
+	* stabs.c (get_stab_string_offset): Fail if there is no string
+	following the stab directive.
+
 2018-04-16  Alan Modra  <amodra@gmail.com>
 
 	* Makefile.am: Remove arm-epoc-pe support.
diff --git a/gas/cond.c b/gas/cond.c
index b74bde7..71680a5 100644
--- a/gas/cond.c
+++ b/gas/cond.c
@@ -28,7 +28,8 @@
    scanned.  */
 struct obstack cond_obstack;
 
-struct file_line {
+struct file_line
+{
   const char *file;
   unsigned int line;
 };
@@ -36,7 +37,8 @@ struct file_line {
 /* We push one of these structures for each .if, and pop it at the
    .endif.  */
 
-struct conditional_frame {
+struct conditional_frame
+{
   /* The source file & line number of the "if".  */
   struct file_line if_file_line;
   /* The source file & line of the "else".  */
@@ -108,9 +110,9 @@ s_ifdef (int test_defined)
       cframe.ignoring = ! (test_defined ^ is_defined);
     }
 
-  current_cframe = ((struct conditional_frame *)
-		    obstack_copy (&cond_obstack, &cframe,
-				  sizeof (cframe)));
+  current_cframe =
+    (struct conditional_frame *) obstack_alloc (&cond_obstack, sizeof cframe);
+  memcpy (current_cframe, &cframe, sizeof cframe);
 
   if (LISTING_SKIP_COND ()
       && cframe.ignoring
@@ -166,8 +168,9 @@ s_if (int arg)
      using an undefined result.  No big deal.  */
   initialize_cframe (&cframe);
   cframe.ignoring = cframe.dead_tree || ! t;
-  current_cframe = ((struct conditional_frame *)
-		    obstack_copy (&cond_obstack, &cframe, sizeof (cframe)));
+  current_cframe =
+    (struct conditional_frame *) obstack_alloc (&cond_obstack, sizeof cframe);
+  memcpy (current_cframe, & cframe, sizeof cframe);
 
   if (LISTING_SKIP_COND ()
       && cframe.ignoring
@@ -202,9 +205,9 @@ s_ifb (int test_blank)
       cframe.ignoring = (test_blank == !is_eol);
     }
 
-  current_cframe = ((struct conditional_frame *)
-		    obstack_copy (&cond_obstack, &cframe,
-				  sizeof (cframe)));
+  current_cframe =
+    (struct conditional_frame *) obstack_alloc (&cond_obstack, sizeof cframe);
+  memcpy (current_cframe, &cframe, sizeof cframe);
 
   if (LISTING_SKIP_COND ()
       && cframe.ignoring
@@ -283,10 +286,11 @@ s_ifc (int arg)
 
   initialize_cframe (&cframe);
   cframe.ignoring = cframe.dead_tree || ! (res ^ arg);
-  current_cframe = ((struct conditional_frame *)
-		    obstack_copy (&cond_obstack, &cframe, sizeof (cframe)));
-
-  if (LISTING_SKIP_COND ()
+  current_cframe =
+    (struct conditional_frame *) obstack_alloc (&cond_obstack, sizeof cframe);
+  memcpy (current_cframe, &cframe, sizeof cframe);
+  
+ if (LISTING_SKIP_COND ()
       && cframe.ignoring
       && (cframe.previous_cframe == NULL
 	  || ! cframe.previous_cframe->ignoring))
@@ -477,8 +481,9 @@ s_ifeqs (int arg)
 
   initialize_cframe (&cframe);
   cframe.ignoring = cframe.dead_tree || ! (res ^ arg);
-  current_cframe = ((struct conditional_frame *)
-		    obstack_copy (&cond_obstack, &cframe, sizeof (cframe)));
+  current_cframe =
+    (struct conditional_frame *) obstack_alloc (&cond_obstack, sizeof cframe);
+  memcpy (current_cframe, &cframe, sizeof cframe);
 
   if (LISTING_SKIP_COND ()
       && cframe.ignoring
@@ -548,6 +553,7 @@ cond_finish_check (int nest)
 	as_bad (_("end of macro inside conditional"));
       else
 	as_bad (_("end of file inside conditional"));
+
       as_bad_where (current_cframe->if_file_line.file,
 		    current_cframe->if_file_line.line,
 		    _("here is the start of the unterminated conditional"));
diff --git a/gas/config/obj-elf.c b/gas/config/obj-elf.c
index 38b79f8..5870447 100644
--- a/gas/config/obj-elf.c
+++ b/gas/config/obj-elf.c
@@ -2471,7 +2471,8 @@ elf_adjust_symtab (void)
       sy = symbol_find_exact (group_name);
       if (!sy
 	  || (sy != symbol_lastP
-	      && (sy->sy_next == NULL
+	      && (sy->sy_flags.sy_local_symbol
+		  || sy->sy_next == NULL
 		  || sy->sy_next->sy_previous != sy)))
 	{
 	  /* Create the symbol now.  */
diff --git a/gas/stabs.c b/gas/stabs.c
index 73d1361..d82de31 100644
--- a/gas/stabs.c
+++ b/gas/stabs.c
@@ -202,6 +202,12 @@ s_stab_generic (int          what,
       int length;
 
       string = demand_copy_C_string (&length);
+      if (string == NULL)
+	{
+	  as_warn (_(".stab%c: missing string"), what);
+	  ignore_rest_of_line ();
+	  return;
+	}
       /* FIXME: We should probably find some other temporary storage
 	 for string, rather than leaking memory if someone else
 	 happens to use the notes obstack.  */