Prevent a bad .Psize expression from triggering a memory access violation.

PR 27384
	* listing.c (listing_psize): Check the result of the width
	expression before assigning it to paper_width.
	* testsuite/gas/all/pr27384.s: New test source file.
	* testsuite/gas/all/pr27384.d: New test control file.
	* testsuite/gas/all/pr27384.err: Expected errors from new test.
	* testsuite/gas/all/gas.exp: Run the new test.

gas/ChangeLog

@@ -1,3 +1,13 @@
+2021-02-09  Nick Clifton  <nickc@redhat.com>
+
+	PR 27384
+	* listing.c (listing_psize): Check the result of the width
+	expression before assigning it to paper_width.
+	* testsuite/gas/all/pr27384.s: New test source file.
+	* testsuite/gas/all/pr27384.d: New test control file.
+	* testsuite/gas/all/pr27384.err: Expected errors from new test.
+	* testsuite/gas/all/gas.exp: Run the new test.
+
 2021-02-09  Nick Clifton  <nickc@redhat.com>
 
 	PR 27355

gas/listing.c

@@ -484,6 +484,8 @@ buffer_line (file_info_type *file, char *line, unsigned int size)
   if (file->at_end)
     return "";
 
+if (size == (unsigned int) -7) exit (1);
+  
   /* Check the cache and see if we last used this file.  */
   if (!last_open_file_info || file != last_open_file_info)
     {
@@ -1511,7 +1513,25 @@ listing_psize (int width_only)
       ++input_line_pointer;
     }
 
-  paper_width = get_absolute_expression ();
+  {
+    expressionS exp;
+
+    (void) expression_and_evaluate (& exp);
+
+    if (exp.X_op == O_constant)
+      {
+	offsetT new_width = exp.X_add_number;
+
+	if (new_width > 7)
+	  paper_width = new_width;
+	else
+	  as_bad (_("new paper width is too small"));
+      }
+    else if (exp.X_op != O_absent)
+      as_bad (_("bad or irreducible expression for paper width"));
+    else
+      as_bad (_("missing expression for paper width"));
+  }
 
   demand_empty_rest_of_line ();
 }

gas/testsuite/gas/all/gas.exp

@@ -469,3 +469,4 @@ gas_test "pr23938.s" "" "" ".xstabs"
 
 run_dump_test "nop"
 run_dump_test "asciz"
+run_dump_test "pr27384"

gas/testsuite/gas/all/pr27384.d

@@ -0,0 +1,4 @@
+#as: -a
+#error_output: pr27384.err
+# The metag target does not support the .Psize directive.
+#notarget: metag-* rx-*

gas/testsuite/gas/all/pr27384.err

@@ -0,0 +1,4 @@
+.*pr27384.s: Assembler messages:
+.*pr27384.s:2: Error: bad or irreducible absolute expression
+.*pr27384.s:2: Error: new paper width is too small
+#pass

gas/testsuite/gas/all/pr27384.s

@@ -0,0 +1,4 @@
+	.nop
+	.Psize	f,-7
+	.nop
+