libxl: fix double free on some config parser errors

If libxlu_cfg_y.y encountered a config file error, the code generated
by bison would sometimes _both_ run the %destructor _and_ call
xlu__cfg_set_store for the same XLU_ConfigSetting* semantic value.
The result would be a double free.

This appears to be because of the use of a mid-rule action.  There is
some discussion of the problems with destructors and mid-rule action
error handling in "(bison)Mid-Rule Actions".  This area is complex and
best avoided.

So fix the bug by abolishing the use of a mid-rule action, which was
in any case not necessary here.

Also while we are there rename the nonterminal rule "setting" to
"assignment", to avoid confusion with the token type "setting", which
had an identically name in a different namespace.  This was especially
confusing because the nonterminal "setting" did not have "setting" as
the type of its semantic value!  (In fact the nonterminal, now called
"assignment", does not have a value so it does not have a value type.)

Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>

1 files changed, 58 insertions, 62 deletions

diff --git a/tools/libxl/libxlu_cfg_y.c b/tools/libxl/libxlu_cfg_y.c
index 7d1f6c8352..521438654d 100644
--- a/tools/libxl/libxlu_cfg_y.c
+++ b/tools/libxl/libxlu_cfg_y.c
@@ -380,11 +380,11 @@ union yyalloc
 /* YYNTOKENS -- Number of terminals.  */
 #define YYNTOKENS  12
 /* YYNNTS -- Number of nonterminals.  */
-#define YYNNTS  10
+#define YYNNTS  9
 /* YYNRULES -- Number of rules.  */
-#define YYNRULES  20
+#define YYNRULES  19
 /* YYNRULES -- Number of states.  */
-#define YYNSTATES  29
+#define YYNSTATES  28
 
 /* YYTRANSLATE(YYLEX) -- Bison symbol number corresponding to YYLEX.  */
 #define YYUNDEFTOK  2
@@ -430,28 +430,26 @@ static const yytype_uint8 yytranslate[] =
    YYRHS.  */
 static const yytype_uint8 yyprhs[] =
 {
-       0,     0,     3,     4,     7,     8,    14,    16,    19,    21,
-      23,    25,    30,    32,    34,    35,    37,    41,    44,    50,
-      51
+       0,     0,     3,     4,     7,    12,    14,    17,    19,    21,
+      23,    28,    30,    32,    33,    35,    39,    42,    48,    49
 };
 
 /* YYRHS -- A `-1'-separated list of the rules' RHS.  */
 static const yytype_int8 yyrhs[] =
 {
-      13,     0,    -1,    -1,    13,    14,    -1,    -1,     3,     7,
-      17,    15,    16,    -1,    16,    -1,     1,     6,    -1,     6,
-      -1,     8,    -1,    18,    -1,     9,    21,    19,    10,    -1,
-       4,    -1,     5,    -1,    -1,    20,    -1,    20,    11,    21,
-      -1,    18,    21,    -1,    20,    11,    21,    18,    21,    -1,
-      -1,    21,     6,    -1
+      13,     0,    -1,    -1,    13,    14,    -1,     3,     7,    16,
+      15,    -1,    15,    -1,     1,     6,    -1,     6,    -1,     8,
+      -1,    17,    -1,     9,    20,    18,    10,    -1,     4,    -1,
+       5,    -1,    -1,    19,    -1,    19,    11,    20,    -1,    17,
+      20,    -1,    19,    11,    20,    17,    20,    -1,    -1,    20,
+       6,    -1
 };
 
 /* YYRLINE[YYN] -- source line where rule number YYN was defined.  */
 static const yytype_uint8 yyrline[] =
 {
-       0,    47,    47,    48,    50,    50,    52,    53,    55,    56,
-      58,    59,    61,    62,    64,    65,    66,    68,    69,    71,
-      73
+       0,    47,    47,    48,    50,    52,    53,    55,    56,    58,
+      59,    61,    62,    64,    65,    66,    68,    69,    71,    73
 };
 #endif
 
@@ -461,7 +459,7 @@ static const yytype_uint8 yyrline[] =
 static const char *const yytname[] =
 {
   "$end", "error", "$undefined", "IDENT", "STRING", "NUMBER", "NEWLINE",
-  "'='", "';'", "'['", "']'", "','", "$accept", "file", "setting", "$@1",
+  "'='", "';'", "'['", "']'", "','", "$accept", "file", "assignment",
   "endstmt", "value", "atom", "valuelist", "values", "nlok", 0
 };
 #endif
@@ -479,17 +477,15 @@ static const yytype_uint16 yytoknum[] =
 /* YYR1[YYN] -- Symbol number of symbol that rule YYN derives.  */
 static const yytype_uint8 yyr1[] =
 {
-       0,    12,    13,    13,    15,    14,    14,    14,    16,    16,
-      17,    17,    18,    18,    19,    19,    19,    20,    20,    21,
-      21
+       0,    12,    13,    13,    14,    14,    14,    15,    15,    16,
+      16,    17,    17,    18,    18,    18,    19,    19,    20,    20
 };
 
 /* YYR2[YYN] -- Number of symbols composing right hand side of rule YYN.  */
 static const yytype_uint8 yyr2[] =
 {
-       0,     2,     0,     2,     0,     5,     1,     2,     1,     1,
-       1,     4,     1,     1,     0,     1,     3,     2,     5,     0,
-       2
+       0,     2,     0,     2,     4,     1,     2,     1,     1,     1,
+       4,     1,     1,     0,     1,     3,     2,     5,     0,     2
 };
 
 /* YYDEFACT[STATE-NAME] -- Default rule to reduce with in state
@@ -497,15 +493,15 @@ static const yytype_uint8 yyr2[] =
    means the default is an error.  */
 static const yytype_uint8 yydefact[] =
 {
-       2,     0,     1,     0,     0,     8,     9,     3,     6,     7,
-       0,    12,    13,    19,     4,    10,    14,     0,    20,    19,
-       0,    15,     5,    17,    11,    19,    16,    19,    18
+       2,     0,     1,     0,     0,     7,     8,     3,     5,     6,
+       0,    11,    12,    18,     0,     9,    13,     4,    19,    18,
+       0,    14,    16,    10,    18,    15,    18,    17
 };
 
 /* YYDEFGOTO[NTERM-NUM].  */
 static const yytype_int8 yydefgoto[] =
 {
-      -1,     1,     7,    17,     8,    14,    15,    20,    21,    16
+      -1,     1,     7,     8,    14,    15,    20,    21,    16
 };
 
 /* YYPACT[STATE-NUM] -- Index in YYTABLE of the portion describing
@@ -513,15 +509,15 @@ static const yytype_int8 yydefgoto[] =
 #define YYPACT_NINF -17
 static const yytype_int8 yypact[] =
 {
-     -17,     1,   -17,    -3,     5,   -17,   -17,   -17,   -17,   -17,
-      10,   -17,   -17,   -17,   -17,   -17,    12,     0,   -17,   -17,
-      11,     9,   -17,    16,   -17,   -17,    12,   -17,    16
+     -17,     2,   -17,    -5,    -3,   -17,   -17,   -17,   -17,   -17,
+      10,   -17,   -17,   -17,    14,   -17,    12,   -17,   -17,   -17,
+      11,    -4,     6,   -17,   -17,    12,   -17,     6
 };
 
 /* YYPGOTO[NTERM-NUM].  */
 static const yytype_int8 yypgoto[] =
 {
-     -17,   -17,   -17,   -17,     6,   -17,   -16,   -17,   -17,   -14
+     -17,   -17,   -17,     9,   -17,   -16,   -17,   -17,   -13
 };
 
 /* YYTABLE[YYPACT[STATE-NUM]].  What to do in state STATE-NUM.  If
@@ -531,25 +527,25 @@ static const yytype_int8 yypgoto[] =
 #define YYTABLE_NINF -1
 static const yytype_uint8 yytable[] =
 {
-      19,     2,     3,     9,     4,    23,     5,     5,     6,     6,
-      27,    26,    10,    28,    11,    12,    11,    12,    18,    13,
-      25,    24,    18,    22
+      19,     9,     2,     3,    10,     4,    22,    24,     5,    26,
+       6,    25,    18,    27,    11,    12,    11,    12,    18,    13,
+       5,    23,     6,    17
 };
 
 static const yytype_uint8 yycheck[] =
 {
-      16,     0,     1,     6,     3,    19,     6,     6,     8,     8,
-      26,    25,     7,    27,     4,     5,     4,     5,     6,     9,
-      11,    10,     6,    17
+      16,     6,     0,     1,     7,     3,    19,    11,     6,    25,
+       8,    24,     6,    26,     4,     5,     4,     5,     6,     9,
+       6,    10,     8,    14
 };
 
 /* YYSTOS[STATE-NUM] -- The (internal number of the) accessing
    symbol of state STATE-NUM.  */
 static const yytype_uint8 yystos[] =
 {
-       0,    13,     0,     1,     3,     6,     8,    14,    16,     6,
-       7,     4,     5,     9,    17,    18,    21,    15,     6,    18,
-      19,    20,    16,    21,    10,    11,    21,    18,    21
+       0,    13,     0,     1,     3,     6,     8,    14,    15,     6,
+       7,     4,     5,     9,    16,    17,    20,    15,     6,    17,
+      18,    19,    20,    10,    11,    20,    17,    20
 };
 
 #define yyerrok		(yyerrstatus = 0)
@@ -1081,7 +1077,7 @@ yydestruct (yymsg, yytype, yyvaluep, yylocationp, ctx)
 	{ free((yyvaluep->string)); };
 
 /* Line 1000 of yacc.c  */
-#line 1085 "libxlu_cfg_y.c"
+#line 1081 "libxlu_cfg_y.c"
 	break;
       case 4: /* "STRING" */
 
@@ -1090,7 +1086,7 @@ yydestruct (yymsg, yytype, yyvaluep, yylocationp, ctx)
 	{ free((yyvaluep->string)); };
 
 /* Line 1000 of yacc.c  */
-#line 1094 "libxlu_cfg_y.c"
+#line 1090 "libxlu_cfg_y.c"
 	break;
       case 5: /* "NUMBER" */
 
@@ -1099,43 +1095,43 @@ yydestruct (yymsg, yytype, yyvaluep, yylocationp, ctx)
 	{ free((yyvaluep->string)); };
 
 /* Line 1000 of yacc.c  */
-#line 1103 "libxlu_cfg_y.c"
+#line 1099 "libxlu_cfg_y.c"
 	break;
-      case 17: /* "value" */
+      case 16: /* "value" */
 
 /* Line 1000 of yacc.c  */
 #line 43 "libxlu_cfg_y.y"
 	{ xlu__cfg_set_free((yyvaluep->setting)); };
 
 /* Line 1000 of yacc.c  */
-#line 1112 "libxlu_cfg_y.c"
+#line 1108 "libxlu_cfg_y.c"
 	break;
-      case 18: /* "atom" */
+      case 17: /* "atom" */
 
 /* Line 1000 of yacc.c  */
 #line 40 "libxlu_cfg_y.y"
 	{ free((yyvaluep->string)); };
 
 /* Line 1000 of yacc.c  */
-#line 1121 "libxlu_cfg_y.c"
+#line 1117 "libxlu_cfg_y.c"
 	break;
-      case 19: /* "valuelist" */
+      case 18: /* "valuelist" */
 
 /* Line 1000 of yacc.c  */
 #line 43 "libxlu_cfg_y.y"
 	{ xlu__cfg_set_free((yyvaluep->setting)); };
 
 /* Line 1000 of yacc.c  */
-#line 1130 "libxlu_cfg_y.c"
+#line 1126 "libxlu_cfg_y.c"
 	break;
-      case 20: /* "values" */
+      case 19: /* "values" */
 
 /* Line 1000 of yacc.c  */
 #line 43 "libxlu_cfg_y.y"
 	{ xlu__cfg_set_free((yyvaluep->setting)); };
 
 /* Line 1000 of yacc.c  */
-#line 1139 "libxlu_cfg_y.c"
+#line 1135 "libxlu_cfg_y.c"
 	break;
 
       default:
@@ -1466,67 +1462,67 @@ yyreduce:
         case 4:
 
 /* Line 1455 of yacc.c  */
-#line 50 "libxlu_cfg_y.y"
-    { xlu__cfg_set_store(ctx,(yyvsp[(1) - (3)].string),(yyvsp[(3) - (3)].setting),(yylsp[(3) - (3)]).first_line); ;}
+#line 51 "libxlu_cfg_y.y"
+    { xlu__cfg_set_store(ctx,(yyvsp[(1) - (4)].string),(yyvsp[(3) - (4)].setting),(yylsp[(3) - (4)]).first_line); ;}
     break;
 
-  case 10:
+  case 9:
 
 /* Line 1455 of yacc.c  */
 #line 58 "libxlu_cfg_y.y"
     { (yyval.setting)= xlu__cfg_set_mk(ctx,1,(yyvsp[(1) - (1)].string)); ;}
     break;
 
-  case 11:
+  case 10:
 
 /* Line 1455 of yacc.c  */
 #line 59 "libxlu_cfg_y.y"
     { (yyval.setting)= (yyvsp[(3) - (4)].setting); ;}
     break;
 
-  case 12:
+  case 11:
 
 /* Line 1455 of yacc.c  */
 #line 61 "libxlu_cfg_y.y"
     { (yyval.string)= (yyvsp[(1) - (1)].string); ;}
     break;
 
-  case 13:
+  case 12:
 
 /* Line 1455 of yacc.c  */
 #line 62 "libxlu_cfg_y.y"
     { (yyval.string)= (yyvsp[(1) - (1)].string); ;}
     break;
 
-  case 14:
+  case 13:
 
 /* Line 1455 of yacc.c  */
 #line 64 "libxlu_cfg_y.y"
     { (yyval.setting)= xlu__cfg_set_mk(ctx,0,0); ;}
     break;
 
-  case 15:
+  case 14:
 
 /* Line 1455 of yacc.c  */
 #line 65 "libxlu_cfg_y.y"
     { (yyval.setting)= (yyvsp[(1) - (1)].setting); ;}
     break;
 
-  case 16:
+  case 15:
 
 /* Line 1455 of yacc.c  */
 #line 66 "libxlu_cfg_y.y"
     { (yyval.setting)= (yyvsp[(1) - (3)].setting); ;}
     break;
 
-  case 17:
+  case 16:
 
 /* Line 1455 of yacc.c  */
 #line 68 "libxlu_cfg_y.y"
     { (yyval.setting)= xlu__cfg_set_mk(ctx,2,(yyvsp[(1) - (2)].string)); ;}
     break;
 
-  case 18:
+  case 17:
 
 /* Line 1455 of yacc.c  */
 #line 69 "libxlu_cfg_y.y"
@@ -1536,7 +1532,7 @@ yyreduce:
 
 
 /* Line 1455 of yacc.c  */
-#line 1540 "libxlu_cfg_y.c"
+#line 1536 "libxlu_cfg_y.c"
       default: break;
     }
   YY_SYMBOL_PRINT ("-> $$ =", yyr1[yyn], &yyval, &yyloc);