Fix use after free in cgen instruction lookup

	* cgen-opc.c (cgen_lookup_insn): Delete buf and base_insn temps.
	Use insn_bytes_value and insn_int_value directly instead.  Don't
	free allocated memory until function exit.

diff --git a/opcodes/ChangeLog b/opcodes/ChangeLog
index 8366d1b..fc6637b 100644 (file)
--- a/opcodes/ChangeLog
+++ b/opcodes/ChangeLog
@@ -1,3 +1,10 @@
+2017-02-11  Stafford Horne  <shorne@gmail.com>
+           Alan Modra  <amodra@gmail.com>
+
+       * cgen-opc.c (cgen_lookup_insn): Delete buf and base_insn temps.
+       Use insn_bytes_value and insn_int_value directly instead.  Don't
+       free allocated memory until function exit.
+
 2017-02-10  Nicholas Piggin  <npiggin@gmail.com>
 
        * ppc-opc.c (powerpc_opcodes) <scv, rfscv>: New mnemonics.

diff --git a/opcodes/cgen-opc.c b/opcodes/cgen-opc.c
index 72b4f05..4299db3 100644 (file)
--- a/opcodes/cgen-opc.c
+++ b/opcodes/cgen-opc.c
@@ -452,18 +452,14 @@ cgen_lookup_insn (CGEN_CPU_DESC cd,
                  CGEN_FIELDS *fields,
                  int alias_p)
 {
-  unsigned char *buf;
-  CGEN_INSN_INT base_insn;
   CGEN_EXTRACT_INFO ex_info;
   CGEN_EXTRACT_INFO *info;
 
   if (cd->int_insn_p)
     {
       info = NULL;
-      buf = (unsigned char *) xmalloc (cd->max_insn_bitsize / 8);
-      cgen_put_insn_value (cd, buf, length, insn_int_value);
-      base_insn = insn_int_value;
-      free (buf);
+      insn_bytes_value = (unsigned char *) xmalloc (cd->max_insn_bitsize / 8);
+      cgen_put_insn_value (cd, insn_bytes_value, length, insn_int_value);
     }
   else
     {
@@ -471,8 +467,7 @@ cgen_lookup_insn (CGEN_CPU_DESC cd,
       ex_info.dis_info = NULL;
       ex_info.insn_bytes = insn_bytes_value;
       ex_info.valid = -1;
-      buf = insn_bytes_value;
-      base_insn = cgen_get_insn_value (cd, buf, length);
+      insn_int_value = cgen_get_insn_value (cd, insn_bytes_value, length);
     }
 
   if (!insn)
@@ -482,7 +477,8 @@ cgen_lookup_insn (CGEN_CPU_DESC cd,
       /* The instructions are stored in hash lists.
         Pick the first one and keep trying until we find the right one.  */
 
-      insn_list = cgen_dis_lookup_insn (cd, (char *) buf, base_insn);
+      insn_list = cgen_dis_lookup_insn (cd, (char *) insn_bytes_value,
+                                       insn_int_value);
       while (insn_list != NULL)
        {
          insn = insn_list->insn;
@@ -494,18 +490,18 @@ cgen_lookup_insn (CGEN_CPU_DESC cd,
              /* Basic bit mask must be correct.  */
              /* ??? May wish to allow target to defer this check until the
                 extract handler.  */
-             if ((base_insn & CGEN_INSN_BASE_MASK (insn))
+             if ((insn_int_value & CGEN_INSN_BASE_MASK (insn))
                  == CGEN_INSN_BASE_VALUE (insn))
                {
                  /* ??? 0 is passed for `pc' */
                  int elength = CGEN_EXTRACT_FN (cd, insn)
-                   (cd, insn, info, base_insn, fields, (bfd_vma) 0);
+                   (cd, insn, info, insn_int_value, fields, (bfd_vma) 0);
                  if (elength > 0)
                    {
                      /* sanity check */
                      if (length != 0 && length != elength)
                        abort ();
-                     return insn;
+                     break;
                    }
                }
            }
@@ -525,15 +521,17 @@ cgen_lookup_insn (CGEN_CPU_DESC cd,
 
       /* ??? 0 is passed for `pc' */
       length = CGEN_EXTRACT_FN (cd, insn)
-       (cd, insn, info, base_insn, fields, (bfd_vma) 0);
+       (cd, insn, info, insn_int_value, fields, (bfd_vma) 0);
       /* Sanity check: must succeed.
         Could relax this later if it ever proves useful.  */
       if (length == 0)
        abort ();
-      return insn;
     }
 
-  return NULL;
+  if (cd->int_insn_p)
+    free (insn_bytes_value);
+
+  return insn;
 }
 
 /* Fill in the operand instances used by INSN whose operands are FIELDS.