check_overflow.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 <stdlib.h>
  11 #include "parse.h"
  12 #include "smatch.h"
  13
  14 static int my_id;
  15
  16 static struct smatch_state *alloc_state(int val)
  17 {
  18         struct smatch_state *state;
  19
  20         state = malloc(sizeof(*state));
  21         state->name = "value";
  22         state->data = malloc(sizeof(int));
  23         *(int *)state->data = val;
  24         return state;
  25 }
  26
  27 static int malloc_size(struct expression *expr)
  28 {
  29         char *name;
  30         struct expression *arg;
  31
  32         if (!expr)
  33                 return 0;
  34
  35         if (expr->type == EXPR_CALL) {
  36                 name = get_variable_from_expr(expr->fn, NULL);
  37                 if (name && !strcmp(name, "kmalloc")) {
  38                         arg = get_argument_from_call_expr(expr->args, 0);
  39                         free_string(name);
  40                         return get_value(arg);
  41                 }
  42                 free_string(name);
  43         } else if (expr->type == EXPR_STRING && expr->string) {
  44                 return expr->string->length * 8;
  45         }
  46         return 0;
  47 }
  48
  49 static void match_declaration(struct symbol *sym)
  50 {
  51         struct symbol *base_type;
  52         char *name;
  53         int size;
  54
  55         if (!sym->ident)
  56                 return;
  57
  58         name = sym->ident->name;
  59         base_type = get_base_type(sym);
  60
  61         if (base_type->type == SYM_ARRAY && base_type->bit_size > 0)
  62                 set_state(name, my_id, NULL, alloc_state(base_type->bit_size / 8));
  63         else {
  64                 size = malloc_size(sym->initializer);
  65                 if (size > 0)
  66                         set_state(name, my_id, NULL, alloc_state(size));
  67         }
  68 }
  69
  70 static void match_assignment(struct expression *expr)
  71 {
  72         char *name;
  73         name = get_variable_from_expr(expr->left, NULL);
  74         if (!name)
  75                 return;
  76         if (malloc_size(expr->right) > 0)
  77                 set_state(name, my_id, NULL, alloc_state(malloc_size(expr->right)));
  78         free_string(name);
  79 }
  80
  81 static void match_fn_call(struct expression *expr)
  82 {
  83         struct expression *dest;
  84         struct expression *data;
  85         char *fn_name;
  86         char *dest_name;
  87         char *data_name;
  88
  89         fn_name = get_variable_from_expr(expr->fn, NULL);
  90         if (!fn_name)
  91                 return;
  92
  93         if (!strcmp(fn_name, "strcpy")) {
  94                 struct smatch_state *dest_state;
  95                 struct smatch_state *data_state;
  96
  97                 dest = get_argument_from_call_expr(expr->args, 0);
  98                 dest_name = get_variable_from_expr(dest, NULL);
  99
 100                 data = get_argument_from_call_expr(expr->args, 1);
 101                 data_name = get_variable_from_expr(data, NULL);
 102
 103                 dest_state = get_state(dest_name, my_id, NULL);
 104                 if (!dest_state || !dest_state->data) {
 105                         free_string(dest_name);
 106                         free_string(data_name);
 107                         return;
 108                 }
 109                 data_state = get_state(data_name, my_id, NULL);
 110                 if (!data_state || !data_state->data) {
 111                         free_string(dest_name);
 112                         free_string(data_name);
 113                         return;
 114                 }
 115
 116                 if (*(int *)dest_state->data < *(int *)data_state->data)
 117                     smatch_msg("error: %s too large for %s", data_name,
 118                                dest_name);
 119                 free_string(dest_name);
 120                 free_string(data_name);
 121         } else if (!strcmp(fn_name, "strncpy")) {
 122                 struct smatch_state *state;
 123                 int needed;
 124                 int has;
 125
 126                 dest = get_argument_from_call_expr(expr->args, 0);
 127                 dest_name = get_variable_from_expr(dest, NULL);
 128
 129                 data = get_argument_from_call_expr(expr->args, 2);
 130                 needed = get_value(data);
 131                 state = get_state(dest_name, my_id, NULL);
 132                 if (!state || !state->data)
 133                         return;
 134                 has = *(int *)state->data;
 135                 if (has < needed)
 136                         smatch_msg("error: %s too small for %d bytes.",
 137                                    dest_name, needed);
 138                 free_string(dest_name);
 139         }
 140         free_string(fn_name);
 141 }
 142
 143 void register_overflow(int id)
 144 {
 145         my_id = id;
 146         add_hook(&match_declaration, DECLARATION_HOOK);
 147         add_hook(&match_assignment, ASSIGNMENT_HOOK);
 148         add_hook(&match_fn_call, FUNCTION_CALL_HOOK);
 149 }