xref: /illumos-gate/usr/src/tools/smatch/src/smatch_buf_comparison.c (revision 1f5207b7604fb44407eb4342aff613f7c4508508)

/*
 * Copyright (C) 2012 Oracle.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
 */

/*
 * The point here is to store that a buffer has x bytes even if we don't know
 * the value of x.
 *
 */

#include "smatch.h"
#include "smatch_extra.h"
#include "smatch_slist.h"

static int size_id;
static int link_id;

/*
 * We need this for code which does:
 *
 *     if (size)
 *         foo = malloc(size);
 *
 * We want to record that the size of "foo" is "size" even after the merge.
 *
 */
static struct smatch_state *unmatched_state(struct sm_state *sm)
{
	struct expression *size_expr;
	sval_t sval;

	if (!sm->state->data)
		return &undefined;
	size_expr = sm->state->data;
	if (!get_implied_value(size_expr, &sval) || sval.value != 0)
		return &undefined;
	return sm->state;
}

static struct smatch_state *merge_links(struct smatch_state *s1, struct smatch_state *s2)
{
	struct expression *expr1, *expr2;

	expr1 = s1->data;
	expr2 = s2->data;

	if (expr1 && expr2 && expr_equiv(expr1, expr2))
		return s1;
	return &merged;
}

static void match_link_modify(struct sm_state *sm, struct expression *mod_expr)
{
	struct expression *expr;
	struct sm_state *tmp;

	expr = sm->state->data;
	if (expr) {
		set_state_expr(size_id, expr, &undefined);
		set_state(link_id, sm->name, sm->sym, &undefined);
		return;
	}

	FOR_EACH_PTR(sm->possible, tmp) {
		expr = tmp->state->data;
		if (expr)
			set_state_expr(size_id, expr, &undefined);
	} END_FOR_EACH_PTR(tmp);
	set_state(link_id, sm->name, sm->sym, &undefined);
}

static struct smatch_state *alloc_expr_state(struct expression *expr)
{
	struct smatch_state *state;
	char *name;

	state = __alloc_smatch_state(0);
	expr = strip_expr(expr);
	name = expr_to_str(expr);
	state->name = alloc_sname(name);
	free_string(name);
	state->data = expr;
	return state;
}

static int bytes_per_element(struct expression *expr)
{
	struct symbol *type;

	type = get_type(expr);
	if (!type)
		return 0;

	if (type->type != SYM_PTR && type->type != SYM_ARRAY)
		return 0;

	type = get_base_type(type);
	return type_bytes(type);
}

static void db_save_type_links(struct expression *array, struct expression *size)
{
	const char *array_name;

	array_name = get_data_info_name(array);
	if (!array_name)
		array_name = "";
	sql_insert_data_info(size, ARRAY_LEN, array_name);
}

static void match_alloc_helper(struct expression *pointer, struct expression *size)
{
	struct expression *tmp;
	struct sm_state *sm;
	sval_t sval;
	int cnt = 0;

	pointer = strip_expr(pointer);
	size = strip_expr(size);
	if (!size || !pointer)
		return;

	while ((tmp = get_assigned_expr(size))) {
		size = strip_expr(tmp);
		if (cnt++ > 5)
			break;
	}

	if (size->type == EXPR_BINOP && size->op == '*') {
		struct expression *mult_left, *mult_right;

		mult_left = strip_expr(size->left);
		mult_right = strip_expr(size->right);

		if (get_implied_value(mult_left, &sval) &&
		    sval.value == bytes_per_element(pointer))
			size = mult_right;
		else if (get_implied_value(mult_right, &sval) &&
		    sval.value == bytes_per_element(pointer))
			size = mult_left;
		else
			return;
	}

	/* Only save links to variables, not fixed sizes */
	if (get_value(size, &sval))
		return;

	db_save_type_links(pointer, size);
	sm = set_state_expr(size_id, pointer, alloc_expr_state(size));
	if (!sm)
		return;
	set_state_expr(link_id, size, alloc_expr_state(pointer));
}

static void match_alloc(const char *fn, struct expression *expr, void *_size_arg)
{
	int size_arg = PTR_INT(_size_arg);
	struct expression *pointer, *call, *arg;

	pointer = strip_expr(expr->left);
	call = strip_expr(expr->right);
	arg = get_argument_from_call_expr(call->args, size_arg);
	match_alloc_helper(pointer, arg);
}

static void match_calloc(const char *fn, struct expression *expr, void *_start_arg)
{
	int start_arg = PTR_INT(_start_arg);
	struct expression *pointer, *call, *arg;
	struct sm_state *tmp;
	sval_t sval;

	pointer = strip_expr(expr->left);
	call = strip_expr(expr->right);
	arg = get_argument_from_call_expr(call->args, start_arg);
	if (get_implied_value(arg, &sval) &&
	    sval.value == bytes_per_element(pointer))
		arg = get_argument_from_call_expr(call->args, start_arg + 1);

	db_save_type_links(pointer, arg);
	tmp = set_state_expr(size_id, pointer, alloc_expr_state(arg));
	if (!tmp)
		return;
	set_state_expr(link_id, arg, alloc_expr_state(pointer));
}

struct expression *get_size_variable(struct expression *buf)
{
	struct smatch_state *state;

	state = get_state_expr(size_id, buf);
	if (state)
		return state->data;
	return NULL;
}

struct expression *get_array_variable(struct expression *size)
{
	struct smatch_state *state;

	state = get_state_expr(link_id, size);
	if (state)
		return state->data;
	return NULL;
}

static void array_check(struct expression *expr)
{
	struct expression *array;
	struct expression *size;
	struct expression *offset;
	char *array_str, *offset_str;

	expr = strip_expr(expr);
	if (!is_array(expr))
		return;

	array = get_array_base(expr);
	size = get_size_variable(array);
	if (!size)
		return;
	offset = get_array_offset(expr);
	if (!possible_comparison(size, SPECIAL_EQUAL, offset))
		return;

	array_str = expr_to_str(array);
	offset_str = expr_to_str(offset);
	sm_warning("potentially one past the end of array '%s[%s]'", array_str, offset_str);
	free_string(array_str);
	free_string(offset_str);
}

struct db_info {
	char *name;
	int ret;
};

static int db_limitter_callback(void *_info, int argc, char **argv, char **azColName)
{
	struct db_info *info = _info;

	/*
	 * If possible the limitters are tied to the struct they limit.  If we
	 * aren't sure which struct they limit then we use them as limitters for
	 * everything.
	 */
	if (!info->name || argv[0][0] == '\0' || strcmp(info->name, argv[0]) == 0)
		info->ret = 1;
	return 0;
}

static char *vsl_to_data_info_name(const char *name, struct var_sym_list *vsl)
{
	struct var_sym *vs;
	struct symbol *type;
	static char buf[80];
	const char *p;

	if (ptr_list_size((struct ptr_list *)vsl) != 1)
		return NULL;
	vs = first_ptr_list((struct ptr_list *)vsl);

	type = get_real_base_type(vs->sym);
	if (!type || type->type != SYM_PTR)
		goto top_level_name;
	type = get_real_base_type(type);
	if (!type || type->type != SYM_STRUCT)
		goto top_level_name;
	if (!type->ident)
		goto top_level_name;

	p = name;
	while ((name = strstr(p, "->")))
		p = name + 2;

	snprintf(buf, sizeof(buf),"(struct %s)->%s", type->ident->name, p);
	return alloc_sname(buf);

top_level_name:
	if (!(vs->sym->ctype.modifiers & MOD_TOPLEVEL))
		return NULL;
	if (vs->sym->ctype.modifiers & MOD_STATIC)
		snprintf(buf, sizeof(buf),"static %s", name);
	else
		snprintf(buf, sizeof(buf),"global %s", name);
	return alloc_sname(buf);
}

int db_var_is_array_limit(struct expression *array, const char *name, struct var_sym_list *vsl)
{
	char *size_name;
	char *array_name = get_data_info_name(array);
	struct db_info db_info = {.name = array_name,};

	size_name = vsl_to_data_info_name(name, vsl);
	if (!size_name)
		return 0;

	run_sql(db_limitter_callback, &db_info,
		"select value from data_info where type = %d and data = '%s';",
		ARRAY_LEN, size_name);

	return db_info.ret;
}

static int known_access_ok_comparison(struct expression *expr)
{
	struct expression *array;
	struct expression *size;
	struct expression *offset;
	int comparison;

	array = get_array_base(expr);
	size = get_size_variable(array);
	if (!size)
		return 0;
	offset = get_array_offset(expr);
	comparison = get_comparison(size, offset);
	if (comparison == '>' || comparison == SPECIAL_UNSIGNED_GT)
		return 1;

	return 0;
}

static int known_access_ok_numbers(struct expression *expr)
{
	struct expression *array;
	struct expression *offset;
	sval_t max;
	int size;

	array = get_array_base(expr);
	offset = get_array_offset(expr);

	size = get_array_size(array);
	if (size <= 0)
		return 0;

	get_absolute_max(offset, &max);
	if (max.uvalue < size)
		return 1;
	return 0;
}

static void array_check_data_info(struct expression *expr)
{
	struct expression *array;
	struct expression *offset;
	struct state_list *slist;
	struct sm_state *sm;
	struct compare_data *comp;
	char *offset_name;
	const char *equal_name = NULL;

	expr = strip_expr(expr);
	if (!is_array(expr))
		return;

	if (known_access_ok_numbers(expr))
		return;
	if (known_access_ok_comparison(expr))
		return;

	array = get_array_base(expr);
	offset = get_array_offset(expr);
	offset_name = expr_to_var(offset);
	if (!offset_name)
		return;
	slist = get_all_possible_equal_comparisons(offset);
	if (!slist)
		goto free;

	FOR_EACH_PTR(slist, sm) {
		comp = sm->state->data;
		if (strcmp(comp->left_var, offset_name) == 0) {
			if (db_var_is_array_limit(array, comp->right_var, comp->right_vsl)) {
				equal_name = comp->right_var;
				break;
			}
		} else if (strcmp(comp->right_var, offset_name) == 0) {
			if (db_var_is_array_limit(array, comp->left_var, comp->left_vsl)) {
				equal_name = comp->left_var;
				break;
			}
		}
	} END_FOR_EACH_PTR(sm);

	if (equal_name) {
		char *array_name = expr_to_str(array);

		sm_warning("potential off by one '%s[]' limit '%s'", array_name, equal_name);
		free_string(array_name);
	}

free:
	free_slist(&slist);
	free_string(offset_name);
}

static void add_allocation_function(const char *func, void *call_back, int param)
{
	add_function_assign_hook(func, call_back, INT_PTR(param));
}

static char *buf_size_param_comparison(struct expression *array, struct expression_list *args)
{
	struct expression *arg;
	struct expression *size;
	static char buf[32];
	int i;

	size = get_size_variable(array);
	if (!size)
		return NULL;

	i = -1;
	FOR_EACH_PTR(args, arg) {
		i++;
		if (arg == array)
			continue;
		if (!expr_equiv(arg, size))
			continue;
		snprintf(buf, sizeof(buf), "==$%d", i);
		return buf;
	} END_FOR_EACH_PTR(arg);

	return NULL;
}

static void match_call(struct expression *call)
{
	struct expression *arg;
	char *compare;
	int param;

	param = -1;
	FOR_EACH_PTR(call->args, arg) {
		param++;
		if (!is_pointer(arg))
			continue;
		compare = buf_size_param_comparison(arg, call->args);
		if (!compare)
			continue;
		sql_insert_caller_info(call, ARRAY_LEN, param, "$", compare);
	} END_FOR_EACH_PTR(arg);
}

static int get_param(int param, char **name, struct symbol **sym)
{
	struct symbol *arg;
	int i;

	i = 0;
	FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, arg) {
		/*
		 * this is a temporary hack to work around a bug (I think in sparse?)
		 * 2.6.37-rc1:fs/reiserfs/journal.o
		 * If there is a function definition without parameter name found
		 * after a function implementation then it causes a crash.
		 * int foo() {}
		 * int bar(char *);
		 */
		if (arg->ident->name < (char *)100)
			continue;
		if (i == param) {
			*name = arg->ident->name;
			*sym = arg;
			return TRUE;
		}
		i++;
	} END_FOR_EACH_PTR(arg);

	return FALSE;
}

static void set_param_compare(const char *array_name, struct symbol *array_sym, char *key, char *value)
{
	struct expression *array_expr;
	struct expression *size_expr;
	struct symbol *size_sym;
	char *size_name;
	long param;
	struct sm_state *tmp;

	if (strncmp(value, "==$", 3) != 0)
		return;
	param = strtol(value + 3, NULL, 10);
	if (!get_param(param, &size_name, &size_sym))
		return;
	array_expr = symbol_expression(array_sym);
	size_expr = symbol_expression(size_sym);

	tmp = set_state_expr(size_id, array_expr, alloc_expr_state(size_expr));
	if (!tmp)
		return;
	set_state_expr(link_id, size_expr, alloc_expr_state(array_expr));
}

static void set_arraysize_arg(const char *array_name, struct symbol *array_sym, char *key, char *value)
{
	struct expression *array_expr;
	struct expression *size_expr;
	struct symbol *size_sym;
	char *size_name;
	long param;
	struct sm_state *tmp;

	param = strtol(key, NULL, 10);
	if (!get_param(param, &size_name, &size_sym))
		return;
	array_expr = symbol_expression(array_sym);
	size_expr = symbol_expression(size_sym);

	tmp = set_state_expr(size_id, array_expr, alloc_expr_state(size_expr));
	if (!tmp)
		return;
	set_state_expr(link_id, size_expr, alloc_expr_state(array_expr));
}

static void munge_start_states(struct statement *stmt)
{
	struct state_list *slist = NULL;
	struct sm_state *sm;
	struct sm_state *poss;

	FOR_EACH_MY_SM(size_id, __get_cur_stree(), sm) {
		if (sm->state != &merged)
			continue;
		/*
		 * screw it.  let's just assume that if one caller passes the
		 * size then they all do.
		 */
		FOR_EACH_PTR(sm->possible, poss) {
			if (poss->state != &merged &&
			    poss->state != &undefined) {
				add_ptr_list(&slist, poss);
				break;
			}
		} END_FOR_EACH_PTR(poss);
	} END_FOR_EACH_SM(sm);

	FOR_EACH_PTR(slist, sm) {
		set_state(size_id, sm->name, sm->sym, sm->state);
	} END_FOR_EACH_PTR(sm);

	free_slist(&slist);
}

void register_buf_comparison(int id)
{
	size_id = id;

	add_unmatched_state_hook(size_id, &unmatched_state);

	add_allocation_function("malloc", &match_alloc, 0);
	add_allocation_function("memdup", &match_alloc, 1);
	add_allocation_function("realloc", &match_alloc, 1);
	if (option_project == PROJ_KERNEL) {
		add_allocation_function("kmalloc", &match_alloc, 0);
		add_allocation_function("kzalloc", &match_alloc, 0);
		add_allocation_function("vmalloc", &match_alloc, 0);
		add_allocation_function("__vmalloc", &match_alloc, 0);
		add_allocation_function("sock_kmalloc", &match_alloc, 1);
		add_allocation_function("kmemdup", &match_alloc, 1);
		add_allocation_function("kmemdup_user", &match_alloc, 1);
		add_allocation_function("dma_alloc_attrs", &match_alloc, 1);
		add_allocation_function("pci_alloc_consistent", &match_alloc, 1);
		add_allocation_function("pci_alloc_coherent", &match_alloc, 1);
		add_allocation_function("devm_kmalloc", &match_alloc, 1);
		add_allocation_function("devm_kzalloc", &match_alloc, 1);
		add_allocation_function("kcalloc", &match_calloc, 0);
		add_allocation_function("devm_kcalloc", &match_calloc, 1);
		add_allocation_function("kmalloc_array", &match_calloc, 0);
		add_allocation_function("krealloc", &match_alloc, 1);
	}

	add_hook(&array_check, OP_HOOK);
	add_hook(&array_check_data_info, OP_HOOK);

	add_hook(&match_call, FUNCTION_CALL_HOOK);
	select_caller_info_hook(set_param_compare, ARRAY_LEN);
	select_caller_info_hook(set_arraysize_arg, ARRAYSIZE_ARG);
	add_hook(&munge_start_states, AFTER_DEF_HOOK);
}

void register_buf_comparison_links(int id)
{
	link_id = id;
	add_merge_hook(link_id, &merge_links);
	add_modification_hook(link_id, &match_link_modify);
}