check_user_data.c

   1 /*
   2  * smatch/check_user_data.c
   3  *
   4  * Copyright (C) 2011 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 /*
  11  * There are a couple checks that try to see if a variable
  12  * comes from the user.  It would be better to unify them
  13  * into one place.  Also it we should follow the data down
  14  * the call paths.  Hence this file.
  15  */
  16
  17 #include "smatch.h"
  18 #include "smatch_slist.h"
  19 #include "smatch_extra.h"
  20
  21 static int my_id;
  22
  23 STATE(capped);
  24 STATE(user_data);
  25
  26 static int is_user_macro(struct expression *expr)
  27 {
  28         return 0;
  29 }
  30
  31 static int db_user_data;
  32 static int db_user_data_callback(void *unused, int argc, char **argv, char **azColName)
  33 {
  34         db_user_data = 1;
  35         return 0;
  36 }
  37
  38 static int passes_user_data(struct expression *expr)
  39 {
  40         struct expression *arg;
  41
  42         FOR_EACH_PTR(expr->args, arg) {
  43                 if (is_user_data(arg))
  44                         return 1;
  45         } END_FOR_EACH_PTR(arg);
  46
  47         return 0;
  48 }
  49
  50 static int is_user_fn_db(struct expression *expr)
  51 {
  52         struct symbol *sym;
  53         static char sql_filter[1024];
  54
  55         if (expr->fn->type != EXPR_SYMBOL)
  56                 return 0;
  57         sym = expr->fn->symbol;
  58         if (!sym)
  59                 return 0;
  60
  61         if (!passes_user_data(expr))
  62                 return 0;
  63
  64         if (sym->ctype.modifiers & MOD_STATIC) {
  65                 snprintf(sql_filter, 1024, "file = '%s' and function = '%s';",
  66                          get_filename(), sym->ident->name);
  67         } else {
  68                 snprintf(sql_filter, 1024, "function = '%s' and static = 0;",
  69                                 sym->ident->name);
  70         }
  71
  72         db_user_data = 0;
  73         run_sql(db_user_data_callback, "select value from return_states where type=%d and %s",
  74                  USER_DATA, sql_filter);
  75         return db_user_data;
  76 }
  77
  78 static int is_user_function(struct expression *expr)
  79 {
  80         if (expr->type != EXPR_CALL)
  81                 return 0;
  82         if (sym_name_is("kmemdup_user", expr->fn))
  83                 return 1;
  84         return is_user_fn_db(expr);
  85 }
  86
  87 static int is_skb_data(struct expression *expr)
  88 {
  89         struct symbol *sym;
  90         char *name;
  91         int len;
  92         int ret = 0;
  93
  94         name = expr_to_var_sym(expr, &sym);
  95         if (!name || !sym)
  96                 goto free;
  97
  98         sym = get_base_type(sym);
  99         if (!sym || sym->type != SYM_PTR)
 100                 goto free;
 101         sym = get_base_type(sym);
 102         if (!sym || sym->type != SYM_STRUCT || !sym->ident)
 103                 goto free;
 104         if (strcmp(sym->ident->name, "sk_buff") != 0)
 105                 goto free;
 106
 107         len = strlen(name);
 108         if (len < 6)
 109                 goto free;
 110         if (strcmp(name + len - 6, "->data") == 0)
 111                 ret = 1;
 112
 113 free:
 114         free_string(name);
 115         return ret;
 116 }
 117
 118 static int in_container_of_macro(struct expression *expr)
 119 {
 120         char *macro;
 121
 122         macro = get_macro_name(expr->pos);
 123
 124         if (!macro)
 125                 return 0;
 126         if (strcmp(macro, "container_of") == 0)
 127                 return 1;
 128         return 0;
 129 }
 130
 131 static int is_user_data_state(struct expression *expr)
 132 {
 133         struct state_list *slist = NULL;
 134         struct sm_state *tmp;
 135         struct symbol *sym;
 136         char *name;
 137         int user = 0;
 138
 139         tmp = get_sm_state_expr(my_id, expr);
 140         if (tmp)
 141                 return slist_has_state(tmp->possible, &user_data);
 142
 143         name = expr_to_str_sym(expr, &sym);
 144         if (!name || !sym)
 145                 goto free;
 146
 147         slist = get_all_states(my_id);
 148         FOR_EACH_PTR(slist, tmp) {
 149                 if (tmp->sym != sym)
 150                         continue;
 151                 if (!strncmp(tmp->name, name, strlen(tmp->name))) {
 152                         if (slist_has_state(tmp->possible, &user_data))
 153                                 user = 1;
 154                         goto free;
 155                 }
 156         } END_FOR_EACH_PTR(tmp);
 157
 158 free:
 159         free_slist(&slist);
 160         free_string(name);
 161         return user;
 162 }
 163
 164 int is_user_data(struct expression *expr)
 165 {
 166         if (!expr)
 167                 return 0;
 168
 169         if (is_capped(expr))
 170                 return 0;
 171         if (in_container_of_macro(expr))
 172                 return 0;
 173
 174         if (is_user_macro(expr))
 175                 return 1;
 176         if (is_user_function(expr))
 177                 return 1;
 178         if (is_skb_data(expr))
 179                 return 1;
 180
 181         expr = strip_expr(expr);  /* this has to come after is_user_macro() */
 182
 183         if (expr->type == EXPR_BINOP) {
 184                 if (is_user_data(expr->left))
 185                         return 1;
 186                 if (is_array(expr))
 187                         return 0;
 188                 if (is_user_data(expr->right))
 189                         return 1;
 190                 return 0;
 191         }
 192         if (expr->type == EXPR_PREOP && (expr->op == '&' || expr->op == '*'))
 193                 expr = strip_expr(expr->unop);
 194
 195         return is_user_data_state(expr);
 196 }
 197
 198 int is_capped_user_data(struct expression *expr)
 199 {
 200         struct sm_state *sm;
 201
 202         sm = get_sm_state_expr(my_id, expr);
 203         if (!sm)
 204                 return 0;
 205         if (slist_has_state(sm->possible, &capped))
 206                 return 1;
 207         return 0;
 208 }
 209
 210 void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 211 {
 212         char fullname[256];
 213
 214         /* sanity check.  this should always be true. */
 215         if (strncmp(key, "$$", 2) != 0)
 216                 return;
 217         snprintf(fullname, 256, "%s%s", name, key + 2);
 218         set_state(my_id, fullname, sym, &user_data);
 219 }
 220
 221 static void match_syscall_definition(struct symbol *sym)
 222 {
 223         struct symbol *arg;
 224         char *macro;
 225
 226         macro = get_macro_name(sym->pos);
 227         if (!macro)
 228                 return;
 229         if (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")) != 0 &&
 230             strncmp("COMPAT_SYSCALL_DEFINE", macro, strlen("COMPAT_SYSCALL_DEFINE")) != 0)
 231                 return;
 232
 233         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 234                 set_state(my_id, arg->ident->name, arg, &user_data);
 235         } END_FOR_EACH_PTR(arg);
 236 }
 237
 238 static void match_condition(struct expression *expr)
 239 {
 240         switch (expr->op) {
 241         case '<':
 242         case SPECIAL_LTE:
 243         case SPECIAL_UNSIGNED_LT:
 244         case SPECIAL_UNSIGNED_LTE:
 245                 if (is_user_data(expr->left))
 246                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 247                 if (is_user_data(expr->right))
 248                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 249                 break;
 250         case '>':
 251         case SPECIAL_GTE:
 252         case SPECIAL_UNSIGNED_GT:
 253         case SPECIAL_UNSIGNED_GTE:
 254                 if (is_user_data(expr->right))
 255                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 256                 if (is_user_data(expr->left))
 257                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 258                 break;
 259         case SPECIAL_EQUAL:
 260                 if (is_user_data(expr->left))
 261                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 262                 if (is_user_data(expr->right))
 263                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 264                 break;
 265         case SPECIAL_NOTEQUAL:
 266                 if (is_user_data(expr->left))
 267                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 268                 if (is_user_data(expr->right))
 269                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 270                 break;
 271         default:
 272                 return;
 273         }
 274 }
 275
 276 static void match_normal_assign(struct expression *expr)
 277 {
 278         if (is_user_data(expr->right))
 279                 set_state_expr(my_id, expr->left, &user_data);
 280         if (expr->op != '=')
 281                 return;
 282         if (is_user_data(expr->left))
 283                 set_state_expr(my_id, expr->left, &capped);
 284 }
 285
 286 static void match_assign(struct expression *expr)
 287 {
 288         char *name;
 289
 290         name = get_macro_name(expr->pos);
 291         if (!name || strcmp(name, "get_user") != 0) {
 292                 match_normal_assign(expr);
 293                 return;
 294         }
 295         name = expr_to_var(expr->right);
 296         if (!name || strcmp(name, "__val_gu") != 0)
 297                 goto free;
 298         set_state_expr(my_id, expr->left, &user_data);
 299 free:
 300         free_string(name);
 301 }
 302
 303 static void match_user_copy(const char *fn, struct expression *expr, void *_param)
 304 {
 305         int param = PTR_INT(_param);
 306         struct expression *dest;
 307
 308         dest = get_argument_from_call_expr(expr->args, param);
 309         dest = strip_expr(dest);
 310         if (!dest)
 311                 return;
 312         /* the first thing I tested this on pass &foo to a function */
 313         set_state_expr(my_id, dest, &user_data);
 314         if (dest->type == EXPR_PREOP && dest->op == '&') {
 315                 /* but normally I'd think it would pass the actual variable */
 316                 dest = dest->unop;
 317                 set_state_expr(my_id, dest, &user_data);
 318         }
 319 }
 320
 321 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 322 {
 323         set_state_expr(my_id, expr->left, &user_data);
 324 }
 325
 326 static void match_assign_userdata(struct expression *expr)
 327 {
 328         if (is_user_data(expr->right))
 329                 set_state_expr(my_id, expr->left, &user_data);
 330 }
 331
 332 static void match_caller_info(struct expression *expr)
 333 {
 334         struct expression *tmp;
 335         int i;
 336
 337         i = 0;
 338         FOR_EACH_PTR(expr->args, tmp) {
 339                 if (is_user_data(tmp))
 340                         sql_insert_caller_info(expr, USER_DATA, i, "$$", "1");
 341                 i++;
 342         } END_FOR_EACH_PTR(tmp);
 343 }
 344
 345 static void struct_member_callback(struct expression *call, int param, char *printed_name, struct smatch_state *state)
 346 {
 347         if (state == &capped)
 348                 return;
 349         sql_insert_caller_info(call, USER_DATA, param, printed_name, "1");
 350 }
 351
 352 static void print_returned_user_data(int return_id, char *return_ranges, struct expression *expr)
 353 {
 354         if (is_user_data(expr)) {
 355                 sql_insert_return_states(return_id, return_ranges, USER_DATA,
 356                                 -1, "", "");
 357         }
 358 }
 359
 360 void check_user_data(int id)
 361 {
 362         if (option_project != PROJ_KERNEL)
 363                 return;
 364         my_id = id;
 365         add_definition_db_callback(set_param_user_data, USER_DATA);
 366         add_hook(&match_syscall_definition, FUNC_DEF_HOOK);
 367         add_hook(&match_condition, CONDITION_HOOK);
 368         add_hook(&match_assign, ASSIGNMENT_HOOK);
 369         add_hook(&match_assign_userdata, ASSIGNMENT_HOOK);
 370         add_function_hook("copy_from_user", &match_user_copy, INT_PTR(0));
 371         add_function_hook("__copy_from_user", &match_user_copy, INT_PTR(0));
 372         add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
 373         add_function_assign_hook("kmemdup_user", &match_user_assign_function, NULL);
 374
 375         add_hook(&match_caller_info, FUNCTION_CALL_HOOK);
 376         add_member_info_callback(my_id, struct_member_callback);
 377         add_returned_state_callback(print_returned_user_data);
 378 }