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 void match_assign(struct expression *expr)
  64 {
  65         struct symbol *sym;
  66         char *name;
  67
  68         name = get_variable_from_expr_simple(expr->left, &sym);
  69         if (!name)
  70                 return;
  71         name = alloc_string(name);
  72         if (is_zero(expr->right))
  73                 set_state(name, my_id, sym, ISNULL);
  74         else
  75                 set_state(name, my_id, sym, NONNULL);
  76 }
  77
  78 /*
  79  * set_new_true_false_states is used in the following conditions
  80  * if (a) { ... if (a) { ... } }
  81  * The problem is that after the second blog a is set to undefined
  82  * even though the second condition is meaning less.  (The second test
  83  * could be a macro for example).
  84  */
  85
  86 static void set_new_true_false_states(const char *name, int my_id,
  87                                       struct symbol *sym, int true_state,
  88                                       int false_state)
  89 {
  90         int tmp;
  91
  92         tmp = get_state(name, my_id, sym);
  93
  94         SM_DEBUG("set_new_stuff called at %d value=%d\n", get_lineno(), tmp);
  95
  96         if (tmp == NOTFOUND || tmp == UNDEFINED || tmp == ISNULL)
  97                 set_true_false_states(name, my_id, sym, true_state, false_state);
  98 }
  99
 100 static void match_condition(struct expression *expr)
 101 {
 102         struct symbol *sym;
 103         char *name;
 104
 105         switch(expr->type) {
 106         case EXPR_SYMBOL:
 107         case EXPR_DEREF:
 108                 name = get_variable_from_expr_simple(expr, &sym);
 109                 if (!name)
 110                         return;
 111                 name = alloc_string(name);
 112                 set_new_true_false_states(name, my_id, sym, NONNULL, ISNULL);
 113                 return;
 114         case EXPR_ASSIGNMENT:
 115                 match_condition(expr->left);
 116                 return;
 117         default:
 118                 return;
 119         }
 120 }
 121
 122 static void match_declarations(struct symbol *sym)
 123 {
 124         if (sym->ident) {
 125                 const char * name;
 126                 name = sym->ident->name;
 127                 if (sym->initializer && is_zero(sym->initializer))
 128                         set_state(name, my_id, sym, ISNULL);
 129         }
 130 }
 131
 132 static int is_array(struct expression *expr)
 133 {
 134         struct symbol *tmp = NULL;
 135         char *name;
 136
 137         name = get_variable_from_expr_simple(expr, NULL);
 138         if (expr->ctype)
 139                 tmp = get_base_type(expr->ctype);
 140         if (!tmp || !name)
 141                 return 0;
 142         if (tmp->type == SYM_PTR)
 143                 tmp = get_base_type(tmp);
 144         if (!tmp)
 145                 return 0;
 146         printf("debug: %s %d\n", name, tmp->type);
 147         if (tmp->ident)
 148                 printf("name %s\n", tmp->ident->name);
 149
 150         return 0;
 151         if (expr->type != EXPR_BINOP || expr->op != '+')
 152                 return 0;
 153         //if (expr->left->ctype && expr->left->ctype.base_type == &ptr_ctype)
 154         //       return 1;
 155         return 0;
 156 }
 157
 158 static void match_dereferences(struct expression *expr)
 159 {
 160         char *deref = NULL;
 161         struct symbol *sym = NULL;
 162
 163         if (expr->op == '*') {
 164                 expr = expr->unop;
 165         } else if (expr->type == EXPR_DEREF && expr->deref->op == '*')
 166                 expr = expr->deref->unop;
 167
 168         /*
 169          * Say you have foo->bar.baz.n
 170          * In that case we really only care about part to the
 171          * left of the ->.
 172          */
 173         while (expr->type == EXPR_DEREF && expr->deref->op != '*')
 174                 expr = expr->deref;
 175
 176         deref = get_variable_from_expr_simple(expr, &sym);
 177         if (!deref)
 178                 return;
 179         deref = alloc_string(deref);
 180
 181         switch(get_state(deref, my_id, sym)) {
 182         case UNDEFINED:
 183                 smatch_msg("Dereferencing Undefined:  %s", deref);
 184                 set_state(deref, my_id, sym, IGNORE);
 185                 break;
 186         case ISNULL:
 187                 /* It turns out that you only get false positives from
 188                    this.  Mostly foo = NULL; sizeof(*foo); */
 189                 /* smatch_msg("Error dereferencing NULL:  %s", deref); */
 190                 set_state(deref, my_id, sym, IGNORE);
 191                 break;
 192         default:
 193                 free_string(deref);
 194                 break;
 195         }
 196 }
 197
 198 void register_null_deref(int id)
 199 {
 200         my_id = id;
 201         add_merge_hook(my_id, &merge_func);
 202         add_hook(&match_function_call_after, FUNCTION_CALL_AFTER_HOOK);
 203         add_hook(&match_assign, ASSIGNMENT_AFTER_HOOK);
 204         add_hook(&match_condition, CONDITION_HOOK);
 205         add_hook(&match_dereferences, DEREF_HOOK);
 206         add_hook(&match_declarations, DECLARATION_HOOK);
 207 }