smatch_buf_size.c

   1 /*
   2  * smatch/smatch_buf_size.c
   3  *
   4  * Copyright (C) 2010 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 #include <stdlib.h>
  11 #include <errno.h>
  12 #include "parse.h"
  13 #include "smatch.h"
  14 #include "smatch_slist.h"
  15 #include "smatch_extra.h"
  16
  17 /*
  18  * This check has two smatch IDs.
  19  * my_size_id - used to store the size of arrays.
  20  * my_strlen_id - track the strlen() of buffers.
  21  */
  22
  23 static int my_size_id;
  24 static int my_strlen_id;
  25
  26 struct limiter {
  27         int buf_arg;
  28         int limit_arg;
  29 };
  30 static struct limiter b0_l2 = {0, 2};
  31
  32 static _Bool params_set[32];
  33
  34 void set_param_buf_size(const char *name, struct symbol *sym, char *key, char *value)
  35 {
  36         char fullname[256];
  37         unsigned int size;
  38
  39         if (strncmp(key, "$$", 2))
  40                 return;
  41
  42         snprintf(fullname, 256, "%s%s", name, key + 2);
  43
  44         errno = 0;
  45         size = strtoul(value, NULL, 10);
  46         if (errno)
  47                 return;
  48
  49         set_state(my_size_id, fullname, sym, alloc_state_num(size));
  50 }
  51
  52 static int get_initializer_size(struct expression *expr)
  53 {
  54         switch (expr->type) {
  55         case EXPR_STRING:
  56                 return expr->string->length;
  57         case EXPR_INITIALIZER: {
  58                 struct expression *tmp;
  59                 int i = 0;
  60                 int max = 0;
  61
  62                 FOR_EACH_PTR(expr->expr_list, tmp) {
  63                         if (tmp->type == EXPR_INDEX && tmp->idx_to > max)
  64                                 max = tmp->idx_to;
  65                         i++;
  66                 } END_FOR_EACH_PTR(tmp);
  67                 if (max)
  68                         return max + 1;
  69                 return i;
  70         }
  71         case EXPR_SYMBOL:
  72                 return get_array_size(expr);
  73         }
  74         return 0;
  75 }
  76
  77 static float get_cast_ratio(struct expression *unstripped)
  78 {
  79         struct expression *start_expr;
  80         struct symbol *start_type;
  81         struct symbol *end_type;
  82         int start_bytes = 0;
  83         int end_bytes = 0;
  84
  85         start_expr = strip_expr(unstripped);
  86         start_type  =  get_type(start_expr);
  87         end_type = get_type(unstripped);
  88         if (!start_type || !end_type)
  89                 return 1;
  90
  91         if (start_type->type == SYM_PTR)
  92                 start_bytes = (get_base_type(start_type))->ctype.alignment;
  93         if (start_type->type == SYM_ARRAY)
  94                 start_bytes = (get_base_type(start_type))->bit_size / 8;
  95         if (end_type->type == SYM_PTR)
  96                 end_bytes = (get_base_type(end_type))->ctype.alignment;
  97         if (end_type->type == SYM_ARRAY)
  98                 end_bytes = (get_base_type(end_type))->bit_size / 8;
  99
 100         if (!start_bytes || !end_bytes)
 101                 return 1;
 102         return start_bytes / end_bytes;
 103 }
 104
 105 int get_array_size(struct expression *expr)
 106 {
 107         struct symbol *tmp;
 108         struct smatch_state *state;
 109         int ret = 0;
 110         float cast_ratio;
 111         long long len;
 112
 113         if (expr->type == EXPR_STRING)
 114                 return expr->string->length;
 115
 116         cast_ratio = get_cast_ratio(expr);
 117         expr = strip_expr(expr);
 118         tmp = get_type(expr);
 119         if (!tmp)
 120                 return 0;
 121
 122         if (tmp->type == SYM_ARRAY) {
 123                 ret = get_expression_value(tmp->array_size);
 124                 /* Dynamically sized array are -1 in sparse */
 125                 if (ret < 0)
 126                         return 0;
 127                 /* People put one element arrays on the end of structs */
 128                 if (ret == 1)
 129                         return 0;
 130                 if (ret)
 131                         return ret * cast_ratio;
 132         }
 133
 134         state = get_state_expr(my_size_id, expr);
 135         if (state == &merged)
 136                 return 0;
 137         if (state && state->data) {
 138                 if (tmp->type == SYM_PTR)
 139                         tmp = get_base_type(tmp);
 140                 if (!tmp->ctype.alignment)
 141                         return 0;
 142                 ret = PTR_INT(state->data) / tmp->ctype.alignment;
 143                 return ret * cast_ratio;
 144         }
 145
 146         if (expr->type == EXPR_SYMBOL && expr->symbol->initializer) {
 147                 if (expr->symbol->initializer != expr) /* int a = a; */
 148                         return get_initializer_size(expr->symbol->initializer) * cast_ratio;
 149         }
 150
 151         state = get_state_expr(my_strlen_id, expr);
 152         if (!state || !state->data)
 153                 return 0;
 154         if (get_implied_max((struct expression *)state->data, &len))
 155                 return len + 1; /* add one because strlen doesn't include the NULL */
 156         return 0;
 157 }
 158
 159 int get_array_size_bytes(struct expression *expr)
 160 {
 161         struct symbol *tmp;
 162         int array_size;
 163         int element_size;
 164
 165         if (expr->type == EXPR_STRING)
 166                 return expr->string->length;
 167
 168         tmp = get_type(expr);
 169         if (!tmp)
 170                 return 0;
 171
 172         if (tmp->type == SYM_ARRAY) {
 173                 tmp = get_base_type(tmp);
 174                 element_size = tmp->bit_size / 8;
 175         } else if (tmp->type == SYM_PTR) {
 176                 tmp = get_base_type(tmp);
 177                 element_size = tmp->ctype.alignment;
 178         } else {
 179                 return 0;
 180         }
 181         array_size = get_array_size(expr);
 182         return array_size * element_size;
 183 }
 184
 185 static void match_strlen_condition(struct expression *expr)
 186 {
 187         struct expression *left;
 188         struct expression *right;
 189         struct expression *str = NULL;
 190         int strlen_left = 0;
 191         int strlen_right = 0;
 192         long long val;
 193         struct smatch_state *true_state = NULL;
 194         struct smatch_state *false_state = NULL;
 195
 196         if (expr->type != EXPR_COMPARE)
 197                 return;
 198         left = strip_expr(expr->left);
 199         right = strip_expr(expr->right);
 200
 201         if (left->type == EXPR_CALL && sym_name_is("strlen", left->fn)) {
 202                 str = get_argument_from_call_expr(left->args, 0);
 203                 strlen_left = 1;
 204         }
 205         if (right->type == EXPR_CALL && sym_name_is("strlen", right->fn)) {
 206                 str = get_argument_from_call_expr(right->args, 0);
 207                 strlen_right = 1;
 208         }
 209
 210         if (!strlen_left && !strlen_right)
 211                 return;
 212         if (strlen_left && strlen_right)
 213                 return;
 214
 215         if (strlen_left) {
 216                 if (!get_value(right, &val))
 217                         return;
 218         }
 219         if (strlen_right) {
 220                 if (!get_value(left, &val))
 221                         return;
 222         }
 223
 224         if (expr->op == SPECIAL_EQUAL) {
 225                 set_true_false_states_expr(my_size_id, str, alloc_state_num(val + 1), NULL);
 226                 return;
 227         }
 228         if (expr->op == SPECIAL_NOTEQUAL) {
 229                 set_true_false_states_expr(my_size_id, str, NULL, alloc_state_num(val + 1));
 230                 return;
 231         }
 232
 233         switch (expr->op) {
 234         case '<':
 235         case SPECIAL_UNSIGNED_LT:
 236                 if (strlen_left)
 237                         true_state = alloc_state_num(val);
 238                 else
 239                         false_state = alloc_state_num(val + 1);
 240                 break;
 241         case SPECIAL_LTE:
 242         case SPECIAL_UNSIGNED_LTE:
 243                 if (strlen_left)
 244                         true_state = alloc_state_num(val + 1);
 245                 else
 246                         false_state = alloc_state_num(val);
 247                 break;
 248         case SPECIAL_GTE:
 249         case SPECIAL_UNSIGNED_GTE:
 250                 if (strlen_left)
 251                         false_state = alloc_state_num(val);
 252                 else
 253                         true_state = alloc_state_num(val + 1);
 254                 break;
 255         case '>':
 256         case SPECIAL_UNSIGNED_GT:
 257                 if (strlen_left)
 258                         false_state = alloc_state_num(val + 1);
 259                 else
 260                         true_state = alloc_state_num(val);
 261                 break;
 262         }
 263         set_true_false_states_expr(my_size_id, str, true_state, false_state);
 264 }
 265
 266 static struct expression *strip_ampersands(struct expression *expr)
 267 {
 268         struct symbol *type;
 269
 270         if (expr->type != EXPR_PREOP)
 271                 return expr;
 272         if (expr->op != '&')
 273                 return expr;
 274         type = get_type(expr->unop);
 275         if (!type || type->type != SYM_ARRAY)
 276                 return expr;
 277         return expr->unop;
 278 }
 279
 280 static void match_array_assignment(struct expression *expr)
 281 {
 282         struct expression *left;
 283         struct expression *right;
 284         int array_size;
 285
 286         if (expr->op != '=')
 287                 return;
 288         left = strip_expr(expr->left);
 289         right = strip_expr(expr->right);
 290         right = strip_ampersands(right);
 291         array_size = get_array_size_bytes(right);
 292         if (array_size)
 293                 set_state_expr(my_size_id, left, alloc_state_num(array_size));
 294 }
 295
 296 static void match_alloc(const char *fn, struct expression *expr, void *_size_arg)
 297 {
 298         int size_arg = PTR_INT(_size_arg);
 299         struct expression *right;
 300         struct expression *arg;
 301         long long bytes;
 302
 303         right = strip_expr(expr->right);
 304         arg = get_argument_from_call_expr(right->args, size_arg);
 305         if (!get_implied_value(arg, &bytes))
 306                 return;
 307         set_state_expr(my_size_id, expr->left, alloc_state_num(bytes));
 308 }
 309
 310 static void match_calloc(const char *fn, struct expression *expr, void *unused)
 311 {
 312         struct expression *right;
 313         struct expression *arg;
 314         long long elements;
 315         long long size;
 316
 317         right = strip_expr(expr->right);
 318         arg = get_argument_from_call_expr(right->args, 0);
 319         if (!get_implied_value(arg, &elements))
 320                 return;
 321         arg = get_argument_from_call_expr(right->args, 1);
 322         if (!get_implied_value(arg, &size))
 323                 return;
 324         set_state_expr(my_size_id, expr->left, alloc_state_num(elements * size));
 325 }
 326
 327 static void match_strlen(const char *fn, struct expression *expr, void *unused)
 328 {
 329         struct expression *right;
 330         struct expression *str;
 331         struct expression *len_expr;
 332         char *len_name;
 333         struct smatch_state *state;
 334
 335         right = strip_expr(expr->right);
 336         str = get_argument_from_call_expr(right->args, 0);
 337         len_expr = strip_expr(expr->left);
 338
 339         len_name = get_variable_from_expr(len_expr, NULL);
 340         if (!len_name)
 341                 return;
 342
 343         state = __alloc_smatch_state(0);
 344         state->name = len_name;
 345         state->data = len_expr;
 346         set_state_expr(my_strlen_id, str, state);
 347 }
 348
 349 static void match_limited(const char *fn, struct expression *expr, void *_limiter)
 350 {
 351         struct limiter *limiter = (struct limiter *)_limiter;
 352         struct expression *dest;
 353         struct expression *size_expr;
 354         long long size;
 355
 356         dest = get_argument_from_call_expr(expr->args, limiter->buf_arg);
 357         size_expr = get_argument_from_call_expr(expr->args, limiter->limit_arg);
 358         if (!get_implied_max(size_expr, &size))
 359                 return;
 360         set_state_expr(my_size_id, dest, alloc_state_num(size));
 361 }
 362
 363 static void match_strcpy(const char *fn, struct expression *expr, void *unused)
 364 {
 365         struct expression fake_assign;
 366
 367         fake_assign.op = '=';
 368         fake_assign.left = get_argument_from_call_expr(expr->args, 0);
 369         fake_assign.right = get_argument_from_call_expr(expr->args, 1);
 370         match_array_assignment(&fake_assign);
 371 }
 372
 373 static void match_strndup(const char *fn, struct expression *expr, void *unused)
 374 {
 375         struct expression *fn_expr;
 376         struct expression *size_expr;
 377         long long size;
 378
 379         fn_expr = strip_expr(expr->right);
 380         size_expr = get_argument_from_call_expr(fn_expr->args, 1);
 381         if (!get_implied_max(size_expr, &size))
 382                 return;
 383
 384         /* It's easy to forget space for the NUL char */
 385         size++;
 386         set_state_expr(my_size_id, expr->left, alloc_state_num(size));
 387 }
 388
 389 static void match_call(struct expression *expr)
 390 {
 391         char *name;
 392         struct expression *arg;
 393         int bytes;
 394         int i;
 395
 396         name = get_fnptr_name(expr->fn);
 397         if (!name)
 398                 return;
 399
 400         i = 0;
 401         FOR_EACH_PTR(expr->args, arg) {
 402                 bytes = get_array_size_bytes(arg);
 403                 if (bytes > 1)
 404                         sm_msg("info: passes_buffer '%s' %d '$$' %d", name, i, bytes);
 405                 i++;
 406         } END_FOR_EACH_PTR(arg);
 407
 408         free_string(name);
 409 }
 410
 411 static void struct_member_callback(char *fn, int param, char *printed_name, struct smatch_state *state)
 412 {
 413         if (state == &merged)
 414                 return;
 415         sm_msg("info: passes_buffer '%s' %d '%s' %s", fn, param, printed_name, state->name);
 416 }
 417
 418 static void match_func_end(struct symbol *sym)
 419 {
 420         memset(params_set, 0, sizeof(params_set));
 421 }
 422
 423 void register_buf_size(int id)
 424 {
 425         my_size_id = id;
 426
 427         add_definition_db_callback(set_param_buf_size, BUF_SIZE);
 428
 429         add_function_assign_hook("malloc", &match_alloc, INT_PTR(0));
 430         add_function_assign_hook("calloc", &match_calloc, NULL);
 431         add_function_assign_hook("memdup", &match_alloc, INT_PTR(1));
 432         if (option_project == PROJ_KERNEL) {
 433                 add_function_assign_hook("kmalloc", &match_alloc, INT_PTR(0));
 434                 add_function_assign_hook("kzalloc", &match_alloc, INT_PTR(0));
 435                 add_function_assign_hook("vmalloc", &match_alloc, INT_PTR(0));
 436                 add_function_assign_hook("__vmalloc", &match_alloc, INT_PTR(0));
 437                 add_function_assign_hook("kcalloc", &match_calloc, NULL);
 438                 add_function_assign_hook("drm_malloc_ab", &match_calloc, NULL);
 439                 add_function_assign_hook("drm_calloc_large", &match_calloc, NULL);
 440                 add_function_assign_hook("kmemdup", &match_alloc, INT_PTR(1));
 441                 add_function_assign_hook("kmemdup_user", &match_alloc, INT_PTR(1));
 442         }
 443         add_hook(&match_array_assignment, ASSIGNMENT_HOOK);
 444         add_hook(&match_strlen_condition, CONDITION_HOOK);
 445         add_function_assign_hook("strlen", &match_strlen, NULL);
 446
 447         add_function_hook("strlcpy", &match_limited, &b0_l2);
 448         add_function_hook("strlcat", &match_limited, &b0_l2);
 449         add_function_hook("memscan", &match_limited, &b0_l2);
 450
 451         add_function_hook("strcpy", &match_strcpy, NULL);
 452
 453         add_function_assign_hook("strndup", match_strndup, NULL);
 454         if (option_project == PROJ_KERNEL)
 455                 add_function_assign_hook("kstrndup", match_strndup, NULL);
 456
 457         if (option_info) {
 458                 add_hook(&match_call, FUNCTION_CALL_HOOK);
 459                 add_member_info_callback(my_size_id, struct_member_callback);
 460         }
 461
 462         add_hook(&match_func_end, END_FUNC_HOOK);
 463 }
 464
 465 void register_strlen(int id)
 466 {
 467         my_strlen_id = id;
 468 }