check_rosenberg.c

   1 /*
   2  * sparse/check_rosenberg.c
   3  *
   4  * Copyright (C) 2011 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 /* Does a search for Dan Rosenberg style info leaks */
  11
  12 /* fixme: struct includes a struct with a hole in it */
  13 /* function is called that clears the struct */
  14
  15 #include "scope.h"
  16 #include "smatch.h"
  17 #include "smatch_function_hashtable.h"
  18 #include "smatch_slist.h"
  19
  20 static int my_id;
  21 extern int check_assigned_expr_id;
  22
  23 STATE(cleared);
  24
  25 static DEFINE_HASHTABLE_INSERT(insert_struct, char, int);
  26 static DEFINE_HASHTABLE_SEARCH(search_struct, char, int);
  27 static struct hashtable *holey_structs;
  28
  29 static char *get_struct_type(struct expression *expr)
  30 {
  31         struct symbol *type;
  32
  33         type = get_type(expr);
  34         if (!type || type->type != SYM_STRUCT || !type->ident)
  35                 return NULL;
  36         return alloc_string(type->ident->name);
  37 }
  38
  39 static int holey_struct(struct expression *expr)
  40 {
  41         char *struct_type = 0;
  42         int ret = 0;
  43
  44         struct_type = get_struct_type(expr);
  45         if (!struct_type)
  46                 return 0;
  47         if (search_struct(holey_structs, struct_type))
  48                 ret = 1;
  49         free_string(struct_type);
  50         return ret;
  51 }
  52
  53 static int has_global_scope(struct expression *expr)
  54 {
  55         struct symbol *sym;
  56
  57         if (expr->type != EXPR_SYMBOL)
  58                 return FALSE;
  59         sym = expr->symbol;
  60         return toplevel(sym->scope);
  61 }
  62
  63 static int was_initialized(struct expression *expr)
  64 {
  65         struct symbol *sym;
  66         char *name;
  67
  68         name = get_variable_from_expr(expr, &sym);
  69         if (!name)
  70                 return 0;
  71         if (sym->initializer)
  72                 return 1;
  73         return 0;
  74 }
  75
  76 static void match_clear(const char *fn, struct expression *expr, void *_arg_no)
  77 {
  78         struct expression *ptr;
  79         int arg_no = PTR_INT(_arg_no);
  80
  81         ptr = get_argument_from_call_expr(expr->args, arg_no);
  82         if (ptr->type != EXPR_PREOP || ptr->op != '&')
  83                 return;
  84         ptr = strip_expr(ptr->unop);
  85         set_state_expr(my_id, ptr, &cleared);
  86 }
  87
  88 static int was_memset(struct expression *expr)
  89 {
  90         if (get_state_expr(my_id, expr) == &cleared)
  91                 return 1;
  92         return 0;
  93 }
  94
  95 static int member_initialized(char *name, struct symbol *outer, struct symbol *member)
  96 {
  97         char buf[256];
  98         struct symbol *base;
  99
 100         base = get_base_type(member);
 101         if (!base || base->type != SYM_BASETYPE || !member->ident)
 102                 return FALSE;
 103
 104         snprintf(buf, 256, "%s.%s", name, member->ident->name);
 105         if (get_state(check_assigned_expr_id, buf, outer))
 106                 return TRUE;
 107
 108         return FALSE;
 109 }
 110
 111 static int member_uninitialized(char *name, struct symbol *outer, struct symbol *member)
 112 {
 113         char buf[256];
 114         struct symbol *base;
 115         struct sm_state *sm;
 116
 117         base = get_base_type(member);
 118         if (!base || base->type != SYM_BASETYPE || !member->ident)
 119                 return FALSE;
 120
 121         snprintf(buf, 256, "%s.%s", name, member->ident->name);
 122         sm = get_sm_state(check_assigned_expr_id, buf, outer);
 123         if (sm && !slist_has_state(sm->possible, &undefined))
 124                 return FALSE;
 125
 126         sm_msg("warn: check that '%s' doesn't leak information", buf);
 127         return TRUE;
 128 }
 129
 130 static void check_members_initialized(struct expression *expr)
 131 {
 132         char *name;
 133         struct symbol *outer;
 134         struct symbol *sym;
 135         struct symbol *tmp;
 136
 137
 138         sym = get_type(expr);
 139         if (!sym || sym->type != SYM_STRUCT)
 140                 return;
 141
 142         name = get_variable_from_expr(expr, &outer);
 143
 144         if (get_state(check_assigned_expr_id, name, outer))
 145                 goto out;
 146
 147         FOR_EACH_PTR(sym->symbol_list, tmp) {
 148                 if (member_initialized(name, outer, tmp))
 149                         goto check;
 150         } END_FOR_EACH_PTR(tmp);
 151         goto out;
 152
 153 check:
 154         FOR_EACH_PTR(sym->symbol_list, tmp) {
 155                 if (member_uninitialized(name, outer, tmp))
 156                         goto out;
 157         } END_FOR_EACH_PTR(tmp);
 158 out:
 159         free_string(name);
 160 }
 161
 162 static void match_copy_to_user(const char *fn, struct expression *expr, void *unused)
 163 {
 164         struct expression *data;
 165
 166         data = get_argument_from_call_expr(expr->args, 1);
 167         if (!data)
 168                 return;
 169         if (data->type != EXPR_PREOP || data->op != '&')
 170                 return;
 171
 172         data = strip_expr(data->unop);
 173         if (data->type != EXPR_SYMBOL)
 174                 return;
 175
 176         if (has_global_scope(data))
 177                 return;
 178         if (was_initialized(data))
 179                 return;
 180         if (was_memset(data))
 181                 return;
 182         if (holey_struct(data)) {
 183                 char *name;
 184
 185                 name = get_variable_from_expr(data, NULL);
 186                 sm_msg("warn: check that '%s' doesn't leak information (struct has holes)", name);
 187                 free_string(name);
 188                 return;
 189         }
 190         check_members_initialized(data);
 191 }
 192
 193 static void register_holey_structs(void)
 194 {
 195         struct token *token;
 196         const char *struct_type;
 197
 198         token = get_tokens_file("kernel.paholes");
 199         if (!token)
 200                 return;
 201         if (token_type(token) != TOKEN_STREAMBEGIN)
 202                 return;
 203         token = token->next;
 204         while (token_type(token) != TOKEN_STREAMEND) {
 205                 if (token_type(token) != TOKEN_IDENT)
 206                         return;
 207                 struct_type = show_ident(token->ident);
 208                 insert_struct(holey_structs, alloc_string(struct_type), INT_PTR(1));
 209                 token = token->next;
 210         }
 211         clear_token_alloc();
 212 }
 213
 214 static void register_clears_argument(void)
 215 {
 216         struct token *token;
 217         const char *func;
 218         int arg;
 219
 220         token = get_tokens_file("kernel.clears_argument");
 221         if (!token)
 222                 return;
 223         if (token_type(token) != TOKEN_STREAMBEGIN)
 224                 return;
 225         token = token->next;
 226         while (token_type(token) != TOKEN_STREAMEND) {
 227                 if (token_type(token) != TOKEN_IDENT)
 228                         return;
 229                 func = show_ident(token->ident);
 230                 token = token->next;
 231                 if (token_type(token) != TOKEN_NUMBER)
 232                         return;
 233                 arg = atoi(token->number);
 234
 235                 add_function_hook(func, &match_clear, INT_PTR(arg));
 236                 token = token->next;
 237         }
 238         clear_token_alloc();
 239 }
 240
 241 void check_rosenberg(int id)
 242 {
 243         if (option_project != PROJ_KERNEL)
 244                 return;
 245         my_id = id;
 246         holey_structs = create_function_hashtable(10000);
 247
 248         register_holey_structs();
 249         register_clears_argument();
 250
 251         add_function_hook("copy_to_user", &match_copy_to_user, NULL);
 252 }