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 = get_variable_from_expr(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 int is_user_data(struct expression *expr)
 119 {
 120         struct state_list *slist = NULL;
 121         struct sm_state *tmp;
 122         struct symbol *sym;
 123         char *name;
 124         int user = 0;
 125
 126         if (!expr)
 127                 return 0;
 128
 129         if (is_capped(expr))
 130                 return 0;
 131
 132         if (is_user_macro(expr))
 133                 return 1;
 134         if (is_user_function(expr))
 135                 return 1;
 136         if (is_skb_data(expr))
 137                 return 1;
 138
 139         expr = strip_expr(expr);  /* this has to come after is_user_macro() */
 140
 141         if (expr->type == EXPR_BINOP) {
 142                 if (is_user_data(expr->left))
 143                         return 1;
 144                 if (is_user_data(expr->right))
 145                         return 1;
 146                 return 0;
 147         }
 148         if (expr->type == EXPR_PREOP && (expr->op == '&' || expr->op == '*'))
 149                 expr = strip_expr(expr->unop);
 150
 151         tmp = get_sm_state_expr(my_id, expr);
 152         if (tmp)
 153                 return slist_has_state(tmp->possible, &user_data);
 154
 155         name = get_variable_from_expr_complex(expr, &sym);
 156         if (!name || !sym)
 157                 goto free;
 158
 159         slist = get_all_states(my_id);
 160         FOR_EACH_PTR(slist, tmp) {
 161                 if (tmp->sym != sym)
 162                         continue;
 163                 if (!strncmp(tmp->name, name, strlen(tmp->name))) {
 164                         if (slist_has_state(tmp->possible, &user_data))
 165                                 user = 1;
 166                         goto free;
 167                 }
 168         } END_FOR_EACH_PTR(tmp);
 169
 170 free:
 171         free_slist(&slist);
 172         free_string(name);
 173         return user;
 174 }
 175
 176 void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 177 {
 178         char fullname[256];
 179
 180         if (strncmp(key, "$$", 2))
 181                 return;
 182         snprintf(fullname, 256, "%s%s", name, key + 2);
 183         set_state(my_id, fullname, sym, &user_data);
 184 }
 185
 186 static void match_syscall_definition(struct symbol *sym)
 187 {
 188         struct symbol *arg;
 189         char *macro;
 190
 191         macro = get_macro_name(sym->pos);
 192         if (!macro)
 193                 return;
 194         if (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")))
 195                 return;
 196
 197         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 198                 set_state(my_id, arg->ident->name, arg, &user_data);
 199         } END_FOR_EACH_PTR(arg);
 200 }
 201
 202 static void match_condition(struct expression *expr)
 203 {
 204         switch (expr->op) {
 205         case '<':
 206         case SPECIAL_LTE:
 207         case SPECIAL_UNSIGNED_LT:
 208         case SPECIAL_UNSIGNED_LTE:
 209                 if (is_user_data(expr->left))
 210                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 211                 if (is_user_data(expr->right))
 212                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 213                 break;
 214         case '>':
 215         case SPECIAL_GTE:
 216         case SPECIAL_UNSIGNED_GT:
 217         case SPECIAL_UNSIGNED_GTE:
 218                 if (is_user_data(expr->right))
 219                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 220                 if (is_user_data(expr->left))
 221                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 222                 break;
 223         case SPECIAL_EQUAL:
 224                 if (is_user_data(expr->left))
 225                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 226                 if (is_user_data(expr->right))
 227                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 228                 break;
 229         case SPECIAL_NOTEQUAL:
 230                 if (is_user_data(expr->left))
 231                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 232                 if (is_user_data(expr->right))
 233                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 234                 break;
 235         default:
 236                 return;
 237         }
 238 }
 239
 240 static void match_normal_assign(struct expression *expr)
 241 {
 242         if (is_user_data(expr->left))
 243                 set_state_expr(my_id, expr->left, &capped);
 244 }
 245
 246 static void match_assign(struct expression *expr)
 247 {
 248         char *name;
 249
 250         name = get_macro_name(expr->pos);
 251         if (!name || strcmp(name, "get_user") != 0) {
 252                 match_normal_assign(expr);
 253                 return;
 254         }
 255         name = get_variable_from_expr(expr->right, NULL);
 256         if (!name || strcmp(name, "__val_gu") != 0)
 257                 goto free;
 258         set_state_expr(my_id, expr->left, &user_data);
 259 free:
 260         free_string(name);
 261 }
 262
 263 static void match_user_copy(const char *fn, struct expression *expr, void *_param)
 264 {
 265         int param = PTR_INT(_param);
 266         struct expression *dest;
 267
 268         dest = get_argument_from_call_expr(expr->args, param);
 269         dest = strip_expr(dest);
 270         if (!dest)
 271                 return;
 272         /* the first thing I tested this on pass &foo to a function */
 273         set_state_expr(my_id, dest, &user_data);
 274         if (dest->type == EXPR_PREOP && dest->op == '&') {
 275                 /* but normally I'd think it would pass the actual variable */
 276                 dest = dest->unop;
 277                 set_state_expr(my_id, dest, &user_data);
 278         }
 279 }
 280
 281 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 282 {
 283         set_state_expr(my_id, expr->left, &user_data);
 284 }
 285
 286 static void match_assign_userdata(struct expression *expr)
 287 {
 288         if (is_user_data(expr->right))
 289                 set_state_expr(my_id, expr->left, &user_data);
 290 }
 291
 292 static void match_caller_info(struct expression *expr)
 293 {
 294         struct expression *tmp;
 295         char *func;
 296         int i;
 297
 298         func = get_fnptr_name(expr->fn);
 299         if (!func)
 300                 return;
 301
 302         i = 0;
 303         FOR_EACH_PTR(expr->args, tmp) {
 304                 if (is_user_data(tmp))
 305                         sm_msg("info: passes user_data '%s' %d '$$' %s", func, i,
 306                                is_static(expr->fn) ? "static" : "global");
 307                 i++;
 308         } END_FOR_EACH_PTR(tmp);
 309 }
 310
 311 static void struct_member_callback(char *fn, char *global_static, int param, char *printed_name, struct smatch_state *state)
 312 {
 313         if (state == &capped)
 314                 return;
 315         sm_msg("info: passes user_data '%s' %d '%s' %s", fn, param, printed_name, global_static);
 316 }
 317
 318 static void match_return(struct expression *expr)
 319 {
 320         if (is_user_data(expr)) {
 321                 struct range_list_sval *rl;
 322
 323                 get_implied_range_list_sval(expr, &rl);
 324                 sm_msg("info: returns_user_data %d '%s' %s",
 325                        get_return_id(), show_ranges_sval(rl), global_static());
 326         }
 327 }
 328
 329 void check_user_data(int id)
 330 {
 331         if (option_project != PROJ_KERNEL)
 332                 return;
 333         my_id = id;
 334         add_definition_db_callback(set_param_user_data, USER_DATA);
 335         add_hook(&match_syscall_definition, FUNC_DEF_HOOK);
 336         add_hook(&match_condition, CONDITION_HOOK);
 337         add_hook(&match_assign, ASSIGNMENT_HOOK);
 338         add_hook(&match_assign_userdata, ASSIGNMENT_HOOK);
 339         add_function_hook("copy_from_user", &match_user_copy, INT_PTR(0));
 340         add_function_hook("__copy_from_user", &match_user_copy, INT_PTR(0));
 341         add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
 342         add_function_assign_hook("kmemdup_user", &match_user_assign_function, NULL);
 343         if (option_info) {
 344                 add_hook(&match_caller_info, FUNCTION_CALL_HOOK);
 345                 add_member_info_callback(my_id, struct_member_callback);
 346                 add_hook(&match_return, RETURN_HOOK);
 347         }
 348 }