From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752497AbeBJVLQ (ORCPT ); Sat, 10 Feb 2018 16:11:16 -0500 Received: from mail-wm0-f68.google.com ([74.125.82.68]:52099 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751145AbeBJVLP (ORCPT ); Sat, 10 Feb 2018 16:11:15 -0500 X-Google-Smtp-Source: AH8x2267buohl6t4jYkoxACCZ3wWp83wgJbRdESo8jUCWRMNgnHo4yu5IMqA17FtANxiN+SZPXkMVQ== Date: Sun, 11 Feb 2018 00:11:10 +0300 From: Alexey Dobriyan To: akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, keescook@chromium.org Subject: [PATCH] kstrtox: make kstrtobool_from_user() very strict Message-ID: <20180210211110.GA24324@avx2> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.7.2 (2016-11-26) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Once upon a time module parameter parsing code accepted 0, 1, y, n, Y and N for boolean values. Gratituous but contained to module code and thus tolerable. Commit ef951599074ba4fad2d0efa0a977129b41e6d203 ("lib: move strtobool() to kstrtobool()") promoted that ugly wart to kstrtobool() and, more importantly, kstrtobool_from_user(). Later set of accepted values was expanded to "on" and "of". Now there are 6+8=14(!) valid strings for a boolean. This patch reduces set of accepted values to "0" and "1" (with optional newline) in spirit with other kstrto*() functions. I'm starting with kstrtobool_from_user() as it is explicitly designed to be used for interacting with userspace. Currently there are 9 users all debug code, so there is hope. Please send before 4.16 so no real users start to depend on verbose behaviour. Signed-off-by: Alexey Dobriyan --- lib/kstrtox.c | 32 +++++++++++++++++++++++++++----- 1 file changed, 27 insertions(+), 5 deletions(-) --- a/lib/kstrtox.c +++ b/lib/kstrtox.c @@ -368,19 +368,41 @@ int kstrtobool(const char *s, bool *res) EXPORT_SYMBOL(kstrtobool); /* - * Since "base" would be a nonsense argument, this open-codes the - * _from_user helper instead of using the helper macro below. + * Convert string to boolean: + * 0 => false + * 1 => true + * 0\n => false + * 1\n => true + * + * Return 0 on success or -E otherwise. */ int kstrtobool_from_user(const char __user *s, size_t count, bool *res) { - /* Longest string needed to differentiate, newline, terminator */ - char buf[4]; + /* 0|1, newline, terminator */ + char buf[3], *p; + bool val; count = min(count, sizeof(buf) - 1); if (copy_from_user(buf, s, count)) return -EFAULT; buf[count] = '\0'; - return kstrtobool(buf, res); + + p = buf; + if (*p == '0') + val = false; + else if (*p == '1') + val = true; + else + return -EINVAL; + p++; + + if (*p == '\n') + p++; + if (*p) + return -EINVAL; + + *res = val; + return 0; } EXPORT_SYMBOL(kstrtobool_from_user);