linux-kernel - Re: [PATCH] staging: rtl8192e: Fix possible buffer overflow in _rtl92e_wx_set

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Date:   Fri, 26 Feb 2021 17:05:26 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Lee Gibson <leegib@...il.com>
Cc:     gregkh@...uxfoundation.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: rtl8192e: Fix possible buffer overflow in
 _rtl92e_wx_set_scan

Here is a v2 of my check.  I've changed it to mark all "->ssid" and
everything in "(struct ieee80211_network)" as protected.  I'm just
playing around with it at this point to explore what works best.  It's
impossible to know until after some results come back.

regards,
dan carpenter

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

static int my_id;

static struct {
	const char *type_name;
	int len;
} member_list[] = {
	{ "(struct ieee80211_network)->ssid", 32 },
	{ "(struct rtllib_network)->ssid", 32 },
};

static void match_memset(const char *fn, struct expression *expr, void *_unused)
{
	struct expression *dest, *size_arg;
	struct range_list *rl;
	char *member_name;
	int dest_size = 0;
	int i;

	dest = get_argument_from_call_expr(expr->args, 0);
	size_arg = get_argument_from_call_expr(expr->args, 2);
	if (!dest || !size_arg)
		return;

	member_name = get_member_name(dest);
	if (!member_name)
		return;

	for (i = 0; i < ARRAY_SIZE(member_list); i++) {
		if (strcmp(member_name, member_list[i].type_name) == 0) {
			dest_size = member_list[i].len;
			goto check;
		}
	}

	if (strstr(member_name, "->ssid"))
		goto check;

	if (strncmp(member_name, "(struct ieee80211_network)", 26) == 0)
		goto check;

	goto free;

check:
	get_absolute_rl(size_arg, &rl);
	if (!dest_size)
		dest_size = get_array_size_bytes(dest);

	if (rl_max(rl).value <= dest_size)
		goto free;

	if (dest_size <= 0 && is_capped(size_arg))
		goto free;

	sm_msg("protected struct member '%s' overflow: rl='%s'", member_name, show_rl(rl));
free:
	free_string(member_name);
}

void check_protected_member(int id)
{
	if (option_project != PROJ_KERNEL)
		return;

	my_id = id;

	add_function_hook("memcpy", &match_memset, NULL);
	add_function_hook("__memcpy", &match_memset, NULL);
}