smatch_points_to_user_data.c

   1 /*
   2  * Copyright (C) 2020 Oracle.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version 2
   7  * of the License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
  16  */
  17
  18 /*
  19  * The problem here is that we can have:
  20  *
  21  * p = skb->data;
  22  *
  23  * In the olden days we would just set "*p = 0-255" which meant that it pointed
  24  * to user data.  But then if we say "if (*p == 11) {" that means that "*p" is
  25  * not user data any more, so then "*(p + 1)" is marked as not user data but it
  26  * is.
  27  *
  28  * So now we've separated out the stuff that points to a user_buf from the other
  29  * user data.
  30  *
  31  * There is a further complication because what if "p" points to a struct?  In
  32  * that case all the struct members are handled by smatch_kernel_user_data.c
  33  * but we still need to keep in mind that "*(p + 1)" is user data.  I'm not
  34  * totally 100% sure how this will work.
  35  *
  36  * Generally a user pointer should be a void pointer, or an array etc.  But if
  37  * it points to a struct that can only be used for pointer math.
  38  *
  39  */
  40
  41 #include "smatch.h"
  42 #include "smatch_slist.h"
  43 #include "smatch_extra.h"
  44
  45 static int my_id;
  46 STATE(user_data);
  47 STATE(user_data_set);
  48
  49 struct user_fn_info {
  50         const char *name;
  51         int type;
  52         int param;
  53         const char *key;
  54 };
  55
  56 // Old stuff that was here, but I no longer believe is user data
  57 // kmap_atomic()
  58 // skb_network_header
  59
  60 //      add_function_hook("memcpy_fromiovec", &match_user_copy, INT_PTR(0));
  61 //      add_function_hook("usb_control_msg", &match_user_copy, INT_PTR(6));
  62
  63 static struct user_fn_info func_table[] = {
  64         { "copy_from_user", USER_PTR_SET, 0, "$" },
  65         { "__copy_from_user", USER_PTR_SET, 0, "$" },
  66         { "kvm_read_guest_virt", USER_PTR_SET, 2, "$" },
  67         { "vpu_iface_receive_msg", USER_PTR_SET, 1, "$" },
  68         { "xdr_stream_decode_u32", USER_PTR_SET, 1, "$" },
  69
  70         { "(struct ksmbd_transport_ops)->read", USER_PTR_SET, 1, "$" },
  71         { "nlmsg_data", USER_PTR_SET, -1, "$" },
  72         { "nla_data", USER_PTR_SET, -1, "$" },
  73         { "memdup_user", USER_PTR_SET, -1, "$" },
  74         { "cfg80211_find_elem_match", USER_PTR_SET, -1, "$" },
  75         { "ieee80211_bss_get_elem", USER_PTR_SET, -1, "$" },
  76         { "cfg80211_find_elem", USER_PTR_SET, -1, "$" },
  77         { "ieee80211_bss_get_ie", USER_PTR_SET, -1, "$" },
  78
  79         { "brcmf_fweh_dequeue_event", USER_PTR_SET, -1, "&$->emsg" },
  80         { "wilc_wlan_rxq_remove", USER_PTR_SET, -1, "$->buffer" },
  81         { "cfg80211_find_vendor_ie", USER_PTR_SET, -1, "$" },
  82
  83         { "xdr_copy_to_scratch", USER_PTR_SET, -1, "$" },
  84         { "xdr_inline_decode", USER_PTR_SET, -1, "$" },
  85         { "ntfs_read_run_nb", USER_PTR_SET, 3, "$" },
  86         { "ntfs_read_bh", USER_PTR_SET, 3, "(0<~$0)" },
  87
  88         { "kstrtoull", USER_PTR_SET, 2, "$" },
  89         { "kstrtoll", USER_PTR_SET, 2, "$" },
  90         { "kstrtoul", USER_PTR_SET, 2, "$" },
  91         { "kstrtol", USER_PTR_SET, 2, "$" },
  92         { "kstrtoint", USER_PTR_SET, 2, "$" },
  93         { "kstrtou64", USER_PTR_SET, 2, "$" },
  94         { "kstrtos64", USER_PTR_SET, 2, "$" },
  95         { "kstrtou32", USER_PTR_SET, 2, "$" },
  96         { "kstrtos32", USER_PTR_SET, 2, "$" },
  97         { "kstrtou16", USER_PTR_SET, 2, "$" },
  98         { "kstrtos16", USER_PTR_SET, 2, "$" },
  99         { "kstrtou8", USER_PTR_SET, 2, "$" },
 100         { "kstrtos8", USER_PTR_SET, 2, "$" },
 101         { "kstrtoull_from_user", USER_PTR_SET, 2, "$" },
 102         { "kstrtoll_from_user", USER_PTR_SET, 2, "$" },
 103         { "kstrtoul_from_user", USER_PTR_SET, 2, "$" },
 104         { "kstrtol_from_user", USER_PTR_SET, 2, "$" },
 105         { "kstrtouint_from_user", USER_PTR_SET, 2, "$" },
 106         { "kstrtoint_from_user", USER_PTR_SET, 2, "$" },
 107         { "kstrtou16_from_user", USER_PTR_SET, 2, "$" },
 108         { "kstrtos16_from_user", USER_PTR_SET, 2, "$" },
 109         { "kstrtou8_from_user", USER_PTR_SET, 2, "$" },
 110         { "kstrtos8_from_user", USER_PTR_SET, 2, "$" },
 111         { "kstrtou64_from_user", USER_PTR_SET, 2, "$" },
 112         { "kstrtos64_from_user", USER_PTR_SET, 2, "$" },
 113         { "kstrtou32_from_user", USER_PTR_SET, 2, "$" },
 114         { "kstrtos32_from_user", USER_PTR_SET, 2, "$" },
 115 };
 116
 117 static struct user_fn_info call_table[] = {
 118         { "__handle_ksmbd_work", USER_DATA, 0, "$->request_buf" },
 119 };
 120
 121 bool is_skb_data(struct expression *expr)
 122 {
 123         struct symbol *sym;
 124
 125         expr = strip_expr(expr);
 126         if (!expr)
 127                 return false;
 128         if (expr->type != EXPR_DEREF)
 129                 return false;
 130
 131         if (!expr->member)
 132                 return false;
 133         if (strcmp(expr->member->name, "data") != 0)
 134                 return false;
 135
 136         sym = get_type(expr->deref);
 137         if (!sym)
 138                 return false;
 139         if (sym->type == SYM_PTR)
 140                 sym = get_real_base_type(sym);
 141         if (!sym || sym->type != SYM_STRUCT || !sym->ident)
 142                 return false;
 143         if (strcmp(sym->ident->name, "sk_buff") != 0)
 144                 return false;
 145
 146         return true;
 147 }
 148
 149 static bool is_array_of_user_data(struct expression *expr)
 150 {
 151         struct expression *deref;
 152         struct symbol *type;
 153
 154         if (expr->type == EXPR_PREOP && expr->op == '&') {
 155                 expr = strip_expr(expr->unop);
 156                 if (expr->type == EXPR_PREOP && expr->op == '*')
 157                         expr = strip_expr(expr->unop);
 158         }
 159
 160         /* This is for array elements &foo->data[4] */
 161         if (expr->type == EXPR_BINOP && expr->op == '+') {
 162                 if (points_to_user_data(expr->left))
 163                         return true;
 164                 if (points_to_user_data(expr->right))
 165                         return true;
 166         }
 167
 168         /* This is for if you have: foo = skb->data; frob(foo->array); */
 169         type = get_type(expr);
 170         if (!type || type->type != SYM_ARRAY)
 171                 return false;
 172
 173         if (expr->type != EXPR_DEREF)
 174                 return false;
 175         deref = strip_expr(expr->deref);
 176         if (deref->type != EXPR_PREOP || deref->op != '*')
 177                 return false;
 178         deref = strip_expr(deref->unop);
 179         return points_to_user_data(deref);
 180 }
 181
 182 static struct expression *remove_addr_stuff(struct expression *expr)
 183 {
 184         /* take "&foo->bar" and return "foo" */
 185         expr = strip_expr(expr);
 186         if (expr->type != EXPR_PREOP || expr->op != '&')
 187                 return expr;
 188         expr = strip_expr(expr->unop);
 189         while (expr && expr->type == EXPR_DEREF) {
 190                 expr = strip_expr(expr->deref);
 191                 if (expr->op == '.')
 192                         continue;
 193                 else
 194                         break;
 195         }
 196         if (expr->type == EXPR_PREOP && expr->op == '*')
 197                 expr = strip_expr(expr->unop);
 198         return expr;
 199 }
 200
 201 static bool math_points_to_user_data(struct expression *expr)
 202 {
 203         struct sm_state *sm;
 204
 205         // TODO: is_array_of_user_data() should probably be handled here
 206
 207         if (expr->type == EXPR_BINOP && expr->op == '+')
 208                 return math_points_to_user_data(expr->left);
 209
 210         expr = remove_addr_stuff(expr);
 211
 212         sm = get_sm_state_expr(my_id, expr);
 213         if (!sm)
 214                 return false;
 215         if (slist_has_state(sm->possible, &user_data) ||
 216             slist_has_state(sm->possible, &user_data_set))
 217                 return true;
 218         return false;
 219 }
 220
 221 bool points_to_user_data(struct expression *expr)
 222 {
 223         struct sm_state *sm;
 224
 225         expr = strip_expr(expr);
 226         if (!expr)
 227                 return false;
 228
 229         if (expr->type == EXPR_POSTOP)
 230                 expr = strip_expr(expr->unop);
 231
 232         if (is_fake_call(expr))
 233                 return false;
 234
 235         if (expr->type == EXPR_ASSIGNMENT)
 236                 return points_to_user_data(expr->left);
 237
 238         if (is_array_of_user_data(expr))
 239                 return true;
 240
 241         if (expr->type == EXPR_BINOP && expr->op == '+')
 242                 return math_points_to_user_data(expr);
 243
 244         if (is_skb_data(expr))
 245                 return true;
 246
 247         // FIXME if you have a struct pointer p then p->foo should be handled
 248         // by smatch_kernel_user_data.c but if you have (p + 1)->foo then this
 249         // should be handled here.
 250         sm = get_sm_state_expr(my_id, expr);
 251         if (!sm)
 252                 return false;
 253         if (slist_has_state(sm->possible, &user_data) ||
 254             slist_has_state(sm->possible, &user_data_set))
 255                 return true;
 256         return false;
 257 }
 258
 259 void set_array_user_ptr(struct expression *expr, bool is_new)
 260 {
 261         struct expression *tmp;
 262
 263         /*
 264          * If you have:
 265          *         p = buf;
 266          *         copy_from_user(p, src, 100);
 267          * At the end, both "p" and "buf" point to user data.
 268          *
 269          */
 270         tmp = get_assigned_expr(expr);
 271         if (tmp)
 272                 set_state_expr(my_id, tmp, is_new ? &user_data_set : &user_data);
 273         set_state_expr(my_id, expr, is_new ? &user_data_set : &user_data);
 274 }
 275
 276 static void match_assign(struct expression *expr)
 277 {
 278         if (is_fake_call(expr->right))
 279                 return;
 280
 281         if (!is_ptr_type(get_type(expr->left)))
 282                 return;
 283
 284         if (points_to_user_data(expr->right)) {
 285                 // FIXME: if the types are different then mark the stuff on
 286                 // the left as user data.
 287                 set_state_expr(my_id, expr->left, &user_data);
 288                 return;
 289         }
 290
 291         // FIXME: just use a modification hook
 292         if (get_state_expr(my_id, expr->left))
 293                 set_state_expr(my_id, expr->left, &undefined);
 294 }
 295
 296 static void match_memcpy(const char *fn, struct expression *expr, void *_unused)
 297 {
 298         struct expression *dest, *src;
 299
 300         dest = get_argument_from_call_expr(expr->args, 0);
 301         src = get_argument_from_call_expr(expr->args, 1);
 302
 303         if (points_to_user_data(src)) {
 304                 set_state_expr(my_id, expr->left, &user_data_set);
 305                 return;
 306         }
 307
 308         if (get_state_expr(my_id, dest))
 309                 set_state_expr(my_id, dest, &undefined);
 310 }
 311
 312 static void fake_assign_helper(struct expression *expr, void *data)
 313 {
 314         struct expression *left = expr->left;
 315         struct symbol *type;
 316         bool set = data;
 317
 318         type = get_type(left);
 319         if (!type)
 320                 return;
 321         if (type->type == SYM_BASETYPE)
 322                 mark_as_user_data(left, set);
 323         else if (type->type == SYM_ARRAY)
 324                 set_array_user_ptr(left, set);
 325 }
 326
 327 static void returns_user_ptr_helper(struct expression *expr, const char *name, struct symbol *sym, bool set)
 328 {
 329         struct expression *call, *arg;
 330
 331         call = expr;
 332         while (call && call->type == EXPR_ASSIGNMENT)
 333                 call = strip_expr(expr->right);
 334         if (!call || call->type != EXPR_CALL)
 335                 return;
 336
 337         if (!set && !we_pass_user_data(call))
 338                 return;
 339
 340         arg = gen_expression_from_name_sym(name, sym);
 341         if (!arg)
 342                 return;
 343
 344         create_recursive_fake_assignments(deref_expression(arg), &fake_assign_helper, INT_PTR(set));
 345
 346         if (arg->type == EXPR_PREOP && arg->op == '&') {
 347                 struct symbol *type;
 348
 349                 type = get_type(arg->unop);
 350                 if (!type || type->type != SYM_ARRAY)
 351                         return;
 352         }
 353
 354         set_state_expr(my_id, arg, set ? &user_data_set : &user_data);
 355 }
 356
 357 static void returns_user_ptr(struct expression *expr, const char *name, struct symbol *sym, void *data)
 358 {
 359         returns_user_ptr_helper(expr, name, sym, false);
 360 }
 361
 362 static void returns_user_ptr_set(struct expression *expr, const char *name, struct symbol *sym, void *data)
 363 {
 364         returns_user_ptr_helper(expr, name, sym, true);
 365 }
 366
 367 static void set_param_user_ptr(const char *name, struct symbol *sym, char *value)
 368 {
 369         set_state(my_id, name, sym, &user_data);
 370 }
 371
 372 static void set_caller_param_key_user_ptr(struct expression *expr, const char *name,
 373                                     struct symbol *sym, void *data)
 374 {
 375         set_state(my_id, name, sym, &user_data);
 376 }
 377
 378 static void caller_info_callback(struct expression *call, int param, char *printed_name, struct sm_state *sm)
 379 {
 380         if (is_socket_stuff(sm->sym))
 381                 return;
 382
 383         if (!slist_has_state(sm->possible, &user_data) &&
 384             !slist_has_state(sm->possible, &user_data_set))
 385                 return;
 386
 387         sql_insert_caller_info(call, USER_PTR, param, printed_name, "");
 388 }
 389
 390 static void return_info_callback(int return_id, char *return_ranges,
 391                                  struct expression *returned_expr,
 392                                  int param,
 393                                  const char *printed_name,
 394                                  struct sm_state *sm)
 395 {
 396         int type;
 397
 398         /* is this even possible? */
 399         if (strcmp(printed_name, "&$") == 0)
 400                 return;
 401
 402         if (is_socket_stuff(sm->sym))
 403                 return;
 404
 405         if (param >= 0) {
 406                 if (!slist_has_state(sm->possible, &user_data_set))
 407                         return;
 408                 type = USER_PTR_SET;
 409         } else {
 410                 if (slist_has_state(sm->possible, &user_data_set))
 411                         type = USER_PTR_SET;
 412                 else if (slist_has_state(sm->possible, &user_data))
 413                         type = USER_PTR;
 414                 else
 415                         return;
 416         }
 417         if (parent_is_gone_var_sym(sm->name, sm->sym))
 418                 return;
 419
 420         sql_insert_return_states(return_id, return_ranges, type,
 421                                  param, printed_name, "");
 422 }
 423
 424 void register_points_to_user_data(int id)
 425 {
 426         struct user_fn_info *info;
 427         int i;
 428
 429         my_id = id;
 430
 431         if (option_project != PROJ_KERNEL)
 432                 return;
 433
 434         add_hook(&match_assign, ASSIGNMENT_HOOK);
 435
 436         add_function_hook("memcpy", &match_memcpy, NULL);
 437         add_function_hook("__memcpy", &match_memcpy, NULL);
 438
 439         add_caller_info_callback(my_id, caller_info_callback);
 440         add_return_info_callback(my_id, return_info_callback);
 441
 442         select_caller_name_sym(set_param_user_ptr, USER_PTR);
 443         for (i = 0; i < ARRAY_SIZE(call_table); i++) {
 444                 info = &call_table[i];
 445                 add_function_param_key_hook_early(info->name,
 446                                                   &set_caller_param_key_user_ptr,
 447                                                   info->param, info->key, info);
 448         }
 449
 450         select_return_param_key(USER_PTR, &returns_user_ptr);
 451         select_return_param_key(USER_PTR_SET, &returns_user_ptr_set);
 452         for (i = 0; i < ARRAY_SIZE(func_table); i++) {
 453                 info = &func_table[i];
 454                 add_function_param_key_hook_late(info->name,
 455                                                  &returns_user_ptr_set,
 456                                                  info->param, info->key, info);
 457         }
 458
 459 }