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_skb_data(struct expression *expr)
  27 {
  28         struct symbol *sym;
  29         char *name;
  30         int len;
  31         int ret = 0;
  32
  33         name = get_variable_from_expr(expr, &sym);
  34         if (!name || !sym)
  35                 goto free;
  36
  37         sym = get_base_type(sym);
  38         if (!sym || sym->type != SYM_PTR)
  39                 goto free;
  40         sym = get_base_type(sym);
  41         if (!sym || sym->type != SYM_STRUCT || !sym->ident)
  42                 goto free;
  43         if (strcmp(sym->ident->name, "sk_buff") != 0)
  44                 goto free;
  45
  46         len = strlen(name);
  47         if (len < 6)
  48                 goto free;
  49         if (strcmp(name + len - 6, "->data") == 0)
  50                 ret = 1;
  51
  52 free:
  53         free_string(name);
  54         return ret;
  55 }
  56
  57 int is_user_data(struct expression *expr)
  58 {
  59         struct state_list *slist = NULL;
  60         struct sm_state *tmp;
  61         struct symbol *sym;
  62         char *name;
  63         int user = 0;
  64
  65         expr = strip_expr(expr);
  66         if (!expr)
  67                 return 0;
  68         if (is_capped(expr))
  69                 return 0;
  70         if (is_skb_data(expr))
  71                 return 1;
  72         if (expr->type == EXPR_BINOP) {
  73                 if (is_user_data(expr->left))
  74                         return 1;
  75                 if (is_user_data(expr->right))
  76                         return 1;
  77                 return 0;
  78         }
  79         if (expr->type == EXPR_PREOP && expr->op == '&')
  80                 expr = strip_expr(expr->unop);
  81
  82         tmp = get_sm_state_expr(my_id, expr);
  83         if (tmp)
  84                 return slist_has_state(tmp->possible, &user_data);
  85
  86         name = get_variable_from_expr_complex(expr, &sym);
  87         if (!name || !sym)
  88                 goto free;
  89
  90         slist = get_all_states(my_id);
  91         FOR_EACH_PTR(slist, tmp) {
  92                 if (tmp->sym != sym)
  93                         continue;
  94                 if (!strncmp(tmp->name, name, strlen(tmp->name))) {
  95                         if (slist_has_state(tmp->possible, &user_data))
  96                                 user = 1;
  97                         goto free;
  98                 }
  99         } END_FOR_EACH_PTR(tmp);
 100
 101 free:
 102         free_slist(&slist);
 103         free_string(name);
 104         return user;
 105 }
 106
 107 void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
 108 {
 109         char fullname[256];
 110
 111         if (strncmp(key, "$$", 2))
 112                 return;
 113         snprintf(fullname, 256, "%s%s", name, key + 2);
 114         set_state(my_id, fullname, sym, &user_data);
 115 }
 116
 117 static void match_condition(struct expression *expr)
 118 {
 119         switch (expr->op) {
 120         case '<':
 121         case SPECIAL_LTE:
 122         case SPECIAL_UNSIGNED_LT:
 123         case SPECIAL_UNSIGNED_LTE:
 124                 if (is_user_data(expr->left))
 125                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 126                 if (is_user_data(expr->right))
 127                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 128                 break;
 129         case '>':
 130         case SPECIAL_GTE:
 131         case SPECIAL_UNSIGNED_GT:
 132         case SPECIAL_UNSIGNED_GTE:
 133                 if (is_user_data(expr->right))
 134                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 135                 if (is_user_data(expr->left))
 136                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 137                 break;
 138         case SPECIAL_EQUAL:
 139                 if (is_user_data(expr->left))
 140                         set_true_false_states_expr(my_id, expr->left, &capped, NULL);
 141                 if (is_user_data(expr->right))
 142                         set_true_false_states_expr(my_id, expr->right, &capped, NULL);
 143                 break;
 144         case SPECIAL_NOTEQUAL:
 145                 if (is_user_data(expr->left))
 146                         set_true_false_states_expr(my_id, expr->left, NULL, &capped);
 147                 if (is_user_data(expr->right))
 148                         set_true_false_states_expr(my_id, expr->right, NULL, &capped);
 149                 break;
 150         default:
 151                 return;
 152         }
 153
 154 }
 155
 156 static void match_normal_assign(struct expression *expr)
 157 {
 158         if (is_user_data(expr->left))
 159                 set_state_expr(my_id, expr->left, &capped);
 160 }
 161
 162 static void match_assign(struct expression *expr)
 163 {
 164         char *name;
 165
 166         name = get_macro_name(expr->pos);
 167         if (!name || strcmp(name, "get_user") != 0) {
 168                 match_normal_assign(expr);
 169                 return;
 170         }
 171         name = get_variable_from_expr(expr->right, NULL);
 172         if (!name || strcmp(name, "__val_gu") != 0)
 173                 goto free;
 174         set_state_expr(my_id, expr->left, &user_data);
 175 free:
 176         free_string(name);
 177 }
 178
 179 static void match_user_copy(const char *fn, struct expression *expr, void *_param)
 180 {
 181         int param = PTR_INT(_param);
 182         struct expression *dest;
 183
 184         dest = get_argument_from_call_expr(expr->args, param);
 185         dest = strip_expr(dest);
 186         if (!dest)
 187                 return;
 188         /* the first thing I tested this on pass &foo to a function */
 189         set_state_expr(my_id, dest, &user_data);
 190         if (dest->type == EXPR_PREOP && dest->op == '&') {
 191                 /* but normally I'd think it would pass the actual variable */
 192                 dest = dest->unop;
 193                 set_state_expr(my_id, dest, &user_data);
 194         }
 195 }
 196
 197 static void match_user_assign_function(const char *fn, struct expression *expr, void *unused)
 198 {
 199         set_state_expr(my_id, expr->left, &user_data);
 200 }
 201
 202 static void match_assign_userdata(struct expression *expr)
 203 {
 204         if (is_user_data(expr->right))
 205                 set_state_expr(my_id, expr->left, &user_data);
 206 }
 207
 208 static void match_caller_info(struct expression *expr)
 209 {
 210         struct expression *tmp;
 211         char *func;
 212         int i;
 213
 214         func = get_fnptr_name(expr->fn);
 215         if (!func)
 216                 return;
 217
 218         i = 0;
 219         FOR_EACH_PTR(expr->args, tmp) {
 220                 if (is_user_data(tmp))
 221                         sm_msg("info: passes user_data %s %d '$$' %s", func, i,
 222                                is_static(expr->fn) ? "static" : "global");
 223                 i++;
 224         } END_FOR_EACH_PTR(tmp);
 225 }
 226
 227 static void struct_member_callback(char *fn, char *global_static, int param, char *printed_name, struct smatch_state *state)
 228 {
 229         if (state == &capped)
 230                 return;
 231         sm_msg("info: passes user_data '%s' %d '%s' %s", fn, param, printed_name, global_static);
 232 }
 233
 234 static void match_return(struct expression *expr)
 235 {
 236         if (is_user_data(expr))
 237                 sm_msg("info: returns_user_data %s", global_static());
 238 }
 239
 240 static int db_user_data;
 241 static int db_user_data_callback(void *unused, int argc, char **argv, char **azColName)
 242 {
 243         db_user_data = 1;
 244         return 0;
 245 }
 246
 247 static int passes_user_data(struct expression *expr)
 248 {
 249         struct expression *arg;
 250
 251         FOR_EACH_PTR(expr->args, arg) {
 252                 if (is_user_data(arg))
 253                         return 1;
 254         } END_FOR_EACH_PTR(arg);
 255
 256         return 0;
 257 }
 258
 259 static void match_call_assignment(struct expression *expr)
 260 {
 261         struct symbol *sym;
 262         static char sql_filter[1024];
 263
 264         if (expr->right->fn->type != EXPR_SYMBOL)
 265                 return;
 266         sym = expr->right->fn->symbol;
 267         if (!sym)
 268                 return;
 269
 270         if (!passes_user_data(expr->right))
 271                 return;
 272
 273         if (sym->ctype.modifiers & MOD_STATIC) {
 274                 snprintf(sql_filter, 1024, "file = '%s' and function = '%s' and type = %d;",
 275                          get_filename(), sym->ident->name, USER_DATA);
 276         } else {
 277                 snprintf(sql_filter, 1024, "function = '%s' and static = 0 and type = %d;",
 278                                 sym->ident->name, USER_DATA);
 279         }
 280
 281         db_user_data = 0;
 282         run_sql(db_user_data_callback, "select value from return_info where %s",
 283                  sql_filter);
 284         if (db_user_data)
 285                 set_state_expr(my_id, expr->left, &user_data);
 286 }
 287
 288 void check_user_data(int id)
 289 {
 290         if (option_project != PROJ_KERNEL)
 291                 return;
 292         my_id = id;
 293         add_definition_db_callback(set_param_user_data, USER_DATA);
 294         add_hook(match_call_assignment, CALL_ASSIGNMENT_HOOK);
 295         add_hook(&match_condition, CONDITION_HOOK);
 296         add_hook(&match_assign, ASSIGNMENT_HOOK);
 297         add_hook(&match_assign_userdata, ASSIGNMENT_HOOK);
 298         add_function_hook("copy_from_user", &match_user_copy, INT_PTR(0));
 299         add_function_hook("__copy_from_user", &match_user_copy, INT_PTR(0));
 300         add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
 301         add_function_assign_hook("kmemdup_user", &match_user_assign_function, NULL);
 302         if (option_info) {
 303                 add_hook(&match_caller_info, FUNCTION_CALL_HOOK);
 304                 add_member_info_callback(my_id, struct_member_callback);
 305                 add_hook(&match_return, RETURN_HOOK);
 306         }
 307 }