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 is_skb_data(struct expression *expr)
  32 {
  33         struct symbol *sym;
  34         char *name;
  35         int len;
  36         int ret = 0;
  37
  38         name = get_variable_from_expr(expr, &sym);
  39         if (!name || !sym)
  40                 goto free;
  41
  42         sym = get_base_type(sym);
  43         if (!sym || sym->type != SYM_PTR)
  44                 goto free;
  45         sym = get_base_type(sym);
  46         if (!sym || sym->type != SYM_STRUCT || !sym->ident)
  47                 goto free;
  48         if (strcmp(sym->ident->name, "sk_buff") != 0)
  49                 goto free;
  50
  51         len = strlen(name);
  52         if (len < 6)
  53                 goto free;
  54         if (strcmp(name + len - 6, "->data") == 0)
  55                 ret = 1;
  56
  57 free:
  58         free_string(name);
  59         return ret;
  60 }
  61
  62 int is_user_data(struct expression *expr)
  63 {
  64         struct state_list *slist = NULL;
  65         struct sm_state *tmp;
  66         struct symbol *sym;
  67         char *name;
  68         int user = 0;
  69
  70         if (!expr)
  71                 return 0;
  72
  73         if (is_capped(expr))
  74                 return 0;
  75
  76         if (is_user_macro(expr))
  77                 return 1;
  78         if (is_skb_data(expr))
  79                 return 1;
  80
  81         expr = strip_expr(expr);  /* this has to come after is_user_macro() */
  82
  83         if (expr->type == EXPR_BINOP) {
  84                 if (is_user_data(expr->left))
  85                         return 1;
  86                 if (is_user_data(expr->right))
  87                         return 1;
  88                 return 0;
  89         }
  90         if (expr->type == EXPR_PREOP && (expr->op == '&' || expr->op == '*'))
  91                 expr = strip_expr(expr->unop);
  92
  93         tmp = get_sm_state_expr(my_id, expr);
  94         if (tmp)
  95                 return slist_has_state(tmp->possible, &user_data);
  96
  97         name = get_variable_from_expr_complex(expr, &sym);
  98         if (!name || !sym)
  99                 goto free;
 100
 101         slist = get_all_states(my_id);
 102         FOR_EACH_PTR(slist, tmp) {
 103                 if (tmp->sym != sym)
 104                         continue;
 105                 if (!strncmp(tmp->name, name, strlen(tmp->name))) {
 106                         if (slist_has_state(tmp->possible, &user_data))
 107                                 user = 1;
 108                         goto free;
 109                 }
 110         } END_FOR_EACH_PTR(tmp);
 111
 112 free:
 113         free_slist(&slist);
 114         free_string(name);
 115         return user;
 116 }
 117
 118 void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 119 {
 120         char fullname[256];
 121
 122         if (strncmp(key, "$$", 2))
 123                 return;
 124         snprintf(fullname, 256, "%s%s", name, key + 2);
 125         set_state(my_id, fullname, sym, &user_data);
 126 }
 127
 128 static void match_syscall_definition(struct symbol *sym)
 129 {
 130         struct symbol *arg;
 131         char *macro;
 132
 133         macro = get_macro_name(sym->pos);
 134         if (!macro)
 135                 return;
 136         if (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")))
 137                 return;
 138
 139         FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
 140                 set_state(my_id, arg->ident->name, arg, &user_data);
 141         } END_FOR_EACH_PTR(arg);
 142 }
 143
 144 static void match_condition(struct expression *expr)
 145 {
 146         switch (expr->op) {
 147         case '<':
 148         case SPECIAL_LTE:
 149         case SPECIAL_UNSIGNED_LT:
 150         case SPECIAL_UNSIGNED_LTE:
 151                 if (is_user_data(expr->left))
 152                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 153                 if (is_user_data(expr->right))
 154                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 155                 break;
 156         case '>':
 157         case SPECIAL_GTE:
 158         case SPECIAL_UNSIGNED_GT:
 159         case SPECIAL_UNSIGNED_GTE:
 160                 if (is_user_data(expr->right))
 161                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 162                 if (is_user_data(expr->left))
 163                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 164                 break;
 165         case SPECIAL_EQUAL:
 166                 if (is_user_data(expr->left))
 167                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 168                 if (is_user_data(expr->right))
 169                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 170                 break;
 171         case SPECIAL_NOTEQUAL:
 172                 if (is_user_data(expr->left))
 173                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 174                 if (is_user_data(expr->right))
 175                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 176                 break;
 177         default:
 178                 return;
 179         }
 180
 181 }
 182
 183 static void match_normal_assign(struct expression *expr)
 184 {
 185         if (is_user_data(expr->left))
 186                 set_state_expr(my_id, expr->left, &capped);
 187 }
 188
 189 static void match_assign(struct expression *expr)
 190 {
 191         char *name;
 192
 193         name = get_macro_name(expr->pos);
 194         if (!name || strcmp(name, "get_user") != 0) {
 195                 match_normal_assign(expr);
 196                 return;
 197         }
 198         name = get_variable_from_expr(expr->right, NULL);
 199         if (!name || strcmp(name, "__val_gu") != 0)
 200                 goto free;
 201         set_state_expr(my_id, expr->left, &user_data);
 202 free:
 203         free_string(name);
 204 }
 205
 206 static void match_user_copy(const char *fn, struct expression *expr, void *_param)
 207 {
 208         int param = PTR_INT(_param);
 209         struct expression *dest;
 210
 211         dest = get_argument_from_call_expr(expr->args, param);
 212         dest = strip_expr(dest);
 213         if (!dest)
 214                 return;
 215         /* the first thing I tested this on pass &foo to a function */
 216         set_state_expr(my_id, dest, &user_data);
 217         if (dest->type == EXPR_PREOP && dest->op == '&') {
 218                 /* but normally I'd think it would pass the actual variable */
 219                 dest = dest->unop;
 220                 set_state_expr(my_id, dest, &user_data);
 221         }
 222 }
 223
 224 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 225 {
 226         set_state_expr(my_id, expr->left, &user_data);
 227 }
 228
 229 static void match_assign_userdata(struct expression *expr)
 230 {
 231         if (is_user_data(expr->right))
 232                 set_state_expr(my_id, expr->left, &user_data);
 233 }
 234
 235 static void match_caller_info(struct expression *expr)
 236 {
 237         struct expression *tmp;
 238         char *func;
 239         int i;
 240
 241         func = get_fnptr_name(expr->fn);
 242         if (!func)
 243                 return;
 244
 245         i = 0;
 246         FOR_EACH_PTR(expr->args, tmp) {
 247                 if (is_user_data(tmp))
 248                         sm_msg("info: passes user_data %s %d '$$' %s", func, i,
 249                                is_static(expr->fn) ? "static" : "global");
 250                 i++;
 251         } END_FOR_EACH_PTR(tmp);
 252 }
 253
 254 static void struct_member_callback(char *fn, char *global_static, int param, char *printed_name, struct smatch_state *state)
 255 {
 256         if (state == &capped)
 257                 return;
 258         sm_msg("info: passes user_data '%s' %d '%s' %s", fn, param, printed_name, global_static);
 259 }
 260
 261 static void match_return(struct expression *expr)
 262 {
 263         if (is_user_data(expr))
 264                 sm_msg("info: returns_user_data %s", global_static());
 265 }
 266
 267 static int db_user_data;
 268 static int db_user_data_callback(void *unused, int argc, char **argv, char **azColName)
 269 {
 270         db_user_data = 1;
 271         return 0;
 272 }
 273
 274 static int passes_user_data(struct expression *expr)
 275 {
 276         struct expression *arg;
 277
 278         FOR_EACH_PTR(expr->args, arg) {
 279                 if (is_user_data(arg))
 280                         return 1;
 281         } END_FOR_EACH_PTR(arg);
 282
 283         return 0;
 284 }
 285
 286 static void match_call_assignment(struct expression *expr)
 287 {
 288         struct symbol *sym;
 289         static char sql_filter[1024];
 290
 291         if (expr->right->fn->type != EXPR_SYMBOL)
 292                 return;
 293         sym = expr->right->fn->symbol;
 294         if (!sym)
 295                 return;
 296
 297         if (!passes_user_data(expr->right))
 298                 return;
 299
 300         if (sym->ctype.modifiers & MOD_STATIC) {
 301                 snprintf(sql_filter, 1024, "file = '%s' and function = '%s' and type = %d;",
 302                          get_filename(), sym->ident->name, USER_DATA);
 303         } else {
 304                 snprintf(sql_filter, 1024, "function = '%s' and static = 0 and type = %d;",
 305                                 sym->ident->name, USER_DATA);
 306         }
 307
 308         db_user_data = 0;
 309         run_sql(db_user_data_callback, "select value from return_info where %s",
 310                  sql_filter);
 311         if (db_user_data)
 312                 set_state_expr(my_id, expr->left, &user_data);
 313 }
 314
 315 void check_user_data(int id)
 316 {
 317         if (option_project != PROJ_KERNEL)
 318                 return;
 319         my_id = id;
 320         add_definition_db_callback(set_param_user_data, USER_DATA);
 321         add_hook(&match_syscall_definition, FUNC_DEF_HOOK);
 322         add_hook(match_call_assignment, CALL_ASSIGNMENT_HOOK);
 323         add_hook(&match_condition, CONDITION_HOOK);
 324         add_hook(&match_assign, ASSIGNMENT_HOOK);
 325         add_hook(&match_assign_userdata, ASSIGNMENT_HOOK);
 326         add_function_hook("copy_from_user", &match_user_copy, INT_PTR(0));
 327         add_function_hook("__copy_from_user", &match_user_copy, INT_PTR(0));
 328         add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
 329         add_function_assign_hook("kmemdup_user", &match_user_assign_function, NULL);
 330         if (option_info) {
 331                 add_hook(&match_caller_info, FUNCTION_CALL_HOOK);
 332                 add_member_info_callback(my_id, struct_member_callback);
 333                 add_hook(&match_return, RETURN_HOOK);
 334         }
 335 }