check_null_deref.c

   1 /*
   2  * sparse/check_deference.c
   3  *
   4  * Copyright (C) 2006 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 #include "token.h"
  11 #include "smatch.h"
  12
  13 static int my_id;
  14
  15 enum states {
  16         ISNULL,
  17         NONNULL,
  18         IGNORE,
  19 };
  20
  21 static int merge_func(const char *name, struct symbol *sym, int s1, int s2)
  22 {
  23         if (s2 == IGNORE)
  24                 return IGNORE;
  25         return UNDEFINED;
  26 }
  27
  28 static void match_function_call_after(struct expression *expr)
  29 {
  30         struct expression *tmp;
  31         struct symbol *sym;
  32         char *name;
  33         char *func = NULL;
  34         int i = 0;
  35
  36         if (expr->fn->type == EXPR_SYMBOL) {
  37                 func = expr->fn->symbol_name->name;
  38         }
  39
  40         FOR_EACH_PTR(expr->args, tmp) {
  41                 if (tmp->op == '&') {
  42                         name = get_variable_from_expr_simple(tmp->unop, &sym);
  43                         if (name) {
  44                                 name = alloc_string(name);
  45                                 set_state(name, my_id, sym, NONNULL);
  46                         }
  47                 } else {
  48                         name = get_variable_from_expr_simple(tmp, &sym);
  49                         if (name && sym) {
  50                                 int state = get_state(name, my_id, sym);
  51                                 if ( state == ISNULL)
  52                                         smatch_msg("Null param %s %d",
  53                                                    func, i);
  54                                 else if (state == UNDEFINED)
  55                                         smatch_msg("Undefined param %s %d",
  56                                                    func, i);
  57                         }
  58                 }
  59                 i++;
  60         } END_FOR_EACH_PTR(tmp);
  61 }
  62
  63 static int is_null(struct expression *expr)
  64 {
  65         if (expr->type == EXPR_VALUE && expr->value == 0)
  66                 return 1;
  67         if (expr->op == '(')
  68                 return is_null(expr->unop);
  69         if (expr->type == EXPR_CAST)
  70                 return is_null(expr->cast_expression);
  71         return 0;
  72 }
  73
  74 static void match_assign(struct expression *expr)
  75 {
  76         struct symbol *sym;
  77         char *name;
  78
  79         name = get_variable_from_expr_simple(expr->left, &sym);
  80         if (!name)
  81                 return;
  82         name = alloc_string(name);
  83         if (is_null(expr->right))
  84                 set_state(name, my_id, sym, ISNULL);
  85         else
  86                 set_state(name, my_id, sym, NONNULL);
  87 }
  88
  89 /*
  90  * set_new_true_false_states is used in the following conditions
  91  * if (a) { ... if (a) { ... } }
  92  * The problem is that after the second blog a is set to undefined
  93  * even though the second condition is meaning less.  (The second test
  94  * could be a macro for example).
  95  */
  96
  97 static void set_new_true_false_states(const char *name, int my_id,
  98                                       struct symbol *sym, int true_state,
  99                                       int false_state)
 100 {
 101         int tmp;
 102
 103         tmp = get_state(name, my_id, sym);
 104
 105         SM_DEBUG("set_new_stuff called at %d value=%d\n", get_lineno(), tmp);
 106
 107         if (tmp == NOTFOUND || tmp == UNDEFINED || tmp == ISNULL)
 108                 set_true_false_states(name, my_id, sym, true_state, false_state);
 109 }
 110
 111 static void match_condition(struct expression *expr)
 112 {
 113         struct symbol *sym;
 114         char *name;
 115
 116         switch(expr->type) {
 117         case EXPR_SYMBOL:
 118         case EXPR_DEREF:
 119                 name = get_variable_from_expr_simple(expr, &sym);
 120                 if (!name)
 121                         return;
 122                 name = alloc_string(name);
 123                 set_new_true_false_states(name, my_id, sym, NONNULL, ISNULL);
 124                 return;
 125         case EXPR_ASSIGNMENT:
 126                 match_condition(expr->left);
 127                 return;
 128         default:
 129                 return;
 130         }
 131 }
 132
 133 static void match_declarations(struct symbol *sym)
 134 {
 135         if (sym->ident) {
 136                 const char * name;
 137                 name = sym->ident->name;
 138                 if (sym->initializer && is_null(sym->initializer))
 139                         set_state(name, my_id, sym, ISNULL);
 140         }
 141 }
 142
 143 static int is_array(struct expression *expr)
 144 {
 145         struct symbol *tmp = NULL;
 146         char *name;
 147
 148         name = get_variable_from_expr_simple(expr, NULL);
 149         if (expr->ctype)
 150                 tmp = get_base_type(expr->ctype);
 151         if (!tmp || !name)
 152                 return 0;
 153         if (tmp->type == SYM_PTR)
 154                 tmp = get_base_type(tmp);
 155         if (!tmp)
 156                 return 0;
 157         printf("debug: %s %d\n", name, tmp->type);
 158         if (tmp->ident)
 159                 printf("name %s\n", tmp->ident->name);
 160
 161         return 0;
 162         if (expr->type != EXPR_BINOP || expr->op != '+')
 163                 return 0;
 164         //if (expr->left->ctype && expr->left->ctype.base_type == &ptr_ctype)
 165         //       return 1;
 166         return 0;
 167 }
 168
 169 static void match_dereferences(struct expression *expr)
 170 {
 171         char *deref = NULL;
 172         struct symbol *sym = NULL;
 173
 174         if (expr->op == '*') {
 175                 expr = expr->unop;
 176         } else if (expr->type == EXPR_DEREF && expr->deref->op == '*')
 177                 expr = expr->deref->unop;
 178
 179         /*
 180          * Say you have foo->bar.baz.n
 181          * In that case we really only care about part to the
 182          * left of the ->.
 183          */
 184         while (expr->type == EXPR_DEREF && expr->deref->op != '*')
 185                 expr = expr->deref;
 186
 187         deref = get_variable_from_expr_simple(expr, &sym);
 188         if (!deref)
 189                 return;
 190         deref = alloc_string(deref);
 191
 192         switch(get_state(deref, my_id, sym)) {
 193         case UNDEFINED:
 194                 smatch_msg("Dereferencing Undefined:  %s", deref);
 195                 set_state(deref, my_id, sym, IGNORE);
 196                 break;
 197         case ISNULL:
 198                 /* It turns out that you only get false positives from
 199                    this.  Mostly foo = NULL; sizeof(*foo); */
 200                 /* smatch_msg("Error dereferencing NULL:  %s", deref); */
 201                 set_state(deref, my_id, sym, IGNORE);
 202                 break;
 203         default:
 204                 free_string(deref);
 205                 break;
 206         }
 207 }
 208
 209 void register_null_deref(int id)
 210 {
 211         my_id = id;
 212         add_merge_hook(my_id, &merge_func);
 213         add_hook(&match_function_call_after, FUNCTION_CALL_AFTER_HOOK);
 214         add_hook(&match_assign, ASSIGNMENT_AFTER_HOOK);
 215         add_hook(&match_condition, CONDITION_HOOK);
 216         add_hook(&match_dereferences, DEREF_HOOK);
 217         add_hook(&match_declarations, DECLARATION_HOOK);
 218 }