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                         return get_value(arg);
  40                 }
  41         } else if (expr->type == EXPR_STRING && expr->string) {
  42                 return expr->string->length * 8;
  43         }
  44         return 0;
  45 }
  46
  47 static void match_declaration(struct symbol *sym)
  48 {
  49         struct symbol *base_type;
  50         char *name;
  51         int size;
  52
  53         if (!sym->ident)
  54                 return;
  55
  56         name = sym->ident->name;
  57         base_type = get_base_type(sym);
  58
  59         if (base_type->type == SYM_ARRAY && base_type->bit_size > 0)
  60                 set_state(name, my_id, NULL, alloc_state(base_type->bit_size / 8));
  61         else {
  62                 size = malloc_size(sym->initializer);
  63                 if (size > 0)
  64                         set_state(name, my_id, NULL, alloc_state(size));
  65         }
  66 }
  67
  68 static void match_assignment(struct expression *expr)
  69 {
  70         char *name;
  71         name = get_variable_from_expr(expr->left, NULL);
  72         if (!name)
  73                 return;
  74         if (malloc_size(expr->right) > 0)
  75                 set_state(name, my_id, NULL, alloc_state(malloc_size(expr->right)));
  76 }
  77
  78 static void match_fn_call(struct expression *expr)
  79 {
  80         struct expression *dest;
  81         struct expression *data;
  82         char *fn_name;
  83         char *dest_name;
  84         char *data_name;
  85
  86         fn_name = get_variable_from_expr(expr->fn, NULL);
  87         if (!fn_name)
  88                 return;
  89
  90         if (!strcmp(fn_name, "strcpy")) {
  91                 struct smatch_state *dest_state;
  92                 struct smatch_state *data_state;
  93
  94                 dest = get_argument_from_call_expr(expr->args, 0);
  95                 dest_name = get_variable_from_expr(dest, NULL);
  96
  97                 data = get_argument_from_call_expr(expr->args, 1);
  98                 data_name = get_variable_from_expr(data, NULL);
  99
 100                 dest_state = get_state(dest_name, my_id, NULL);
 101                 if (!dest_state || !dest_state->data) {
 102                         return;
 103                 }
 104                 data_state = get_state(data_name, my_id, NULL);
 105                 if (!data_state || !data_state->data) {
 106                         return;
 107                 }
 108
 109                 if (*(int *)dest_state->data < *(int *)data_state->data)
 110                     smatch_msg("Error %s too large for %s", data_name,
 111                                dest_name);
 112         } else if (!strcmp(fn_name, "strncpy")) {
 113                 struct smatch_state *state;
 114                 int needed;
 115                 int has;
 116
 117                 dest = get_argument_from_call_expr(expr->args, 0);
 118                 dest_name = get_variable_from_expr(dest, NULL);
 119
 120                 data = get_argument_from_call_expr(expr->args, 2);
 121                 needed = get_value(data);
 122                 state = get_state(dest_name, my_id, NULL);
 123                 if (!state || !state->data)
 124                         return;
 125                 has = *(int *)state->data;
 126                 if (has < needed)
 127                         smatch_msg("Error %s too small for %d bytes.",
 128                                    dest_name, needed);
 129         }
 130 }
 131
 132 void register_overflow(int id)
 133 {
 134         my_id = id;
 135         add_hook(&match_declaration, DECLARATION_HOOK);
 136         add_hook(&match_assignment, ASSIGNMENT_HOOK);
 137         add_hook(&match_fn_call, FUNCTION_CALL_HOOK);
 138 }