From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 91FA1C4BA3B for ; Thu, 27 Feb 2020 13:02:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6F07E24693 for ; Thu, 27 Feb 2020 13:02:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729139AbgB0NC1 (ORCPT ); Thu, 27 Feb 2020 08:02:27 -0500 Received: from mx2.suse.de ([195.135.220.15]:37336 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729121AbgB0NC1 (ORCPT ); Thu, 27 Feb 2020 08:02:27 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 7AF68B310; Thu, 27 Feb 2020 13:02:25 +0000 (UTC) From: Petr Mladek To: Andy Shevchenko , Sergey Senozhatsky , Steven Rostedt Cc: Rasmus Villemoes , Sergey Senozhatsky , linux-kernel@vger.kernel.org, =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= , Ilya Dryomov , Kees Cook , "Tobin C . Harding" , Petr Mladek Subject: [PATCH 1/3] lib/test_printf: Clean up test of hashed pointers Date: Thu, 27 Feb 2020 14:01:21 +0100 Message-Id: <20200227130123.32442-2-pmladek@suse.com> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20200227130123.32442-1-pmladek@suse.com> References: <20200227130123.32442-1-pmladek@suse.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The commit ad67b74d2469d9b82a ("printk: hash addresses printed with %p") helps to prevent leaking kernel addresses. The testing of this functionality is a bit problematic because the output depends on a random key that is generated during boot. Though, it is still possible to check some aspects: + output string length + hash differs from the original pointer value + top half bits are zeroed on 64-bit systems This is currently done by a maze of functions: + It is hard to follow. + Some code is duplicated, e.g. the check for initialized crng. + The zeroed top half bits are tested only with one hardcoded PTR. + plain() increments "failed_tests" but not "total_tests". + The generic test_hashed() does not touch number of tests at all. Move all the checks into test_hashed() so that they are done for any given pointer that should get hashed. Also handle test counters and internal errors the same way as the existing test() function. Signed-off-by: Petr Mladek --- lib/test_printf.c | 130 ++++++++++++++++++------------------------------------ 1 file changed, 42 insertions(+), 88 deletions(-) diff --git a/lib/test_printf.c b/lib/test_printf.c index 2d9f520d2f27..6fa6fb606554 100644 --- a/lib/test_printf.c +++ b/lib/test_printf.c @@ -215,29 +215,6 @@ test_string(void) #define PTR_VAL_NO_CRNG "(____ptrval____)" #define ZEROS "00000000" /* hex 32 zero bits */ -static int __init -plain_format(void) -{ - char buf[PLAIN_BUF_SIZE]; - int nchars; - - nchars = snprintf(buf, PLAIN_BUF_SIZE, "%p", PTR); - - if (nchars != PTR_WIDTH) - return -1; - - if (strncmp(buf, PTR_VAL_NO_CRNG, PTR_WIDTH) == 0) { - pr_warn("crng possibly not yet initialized. plain 'p' buffer contains \"%s\"", - PTR_VAL_NO_CRNG); - return 0; - } - - if (strncmp(buf, ZEROS, strlen(ZEROS)) != 0) - return -1; - - return 0; -} - #else #define PTR_WIDTH 8 @@ -246,88 +223,65 @@ plain_format(void) #define PTR_VAL_NO_CRNG "(ptrval)" #define ZEROS "" -static int __init -plain_format(void) -{ - /* Format is implicitly tested for 32 bit machines by plain_hash() */ - return 0; -} - #endif /* BITS_PER_LONG == 64 */ -static int __init -plain_hash_to_buffer(const void *p, char *buf, size_t len) +static void __init +test_hashed(const char *fmt, const void *p) { + char real[PLAIN_BUF_SIZE]; + char hash[PLAIN_BUF_SIZE]; int nchars; - nchars = snprintf(buf, len, "%p", p); - - if (nchars != PTR_WIDTH) - return -1; + total_tests++; - if (strncmp(buf, PTR_VAL_NO_CRNG, PTR_WIDTH) == 0) { - pr_warn("crng possibly not yet initialized. plain 'p' buffer contains \"%s\"", - PTR_VAL_NO_CRNG); - return 0; + nchars = snprintf(real, sizeof(real), "%px", p); + if (nchars != PTR_WIDTH) { + pr_err("error in test suite: vsprintf(\"%%px\", p) returned number of characters %d, expected %d\n", + nchars, PTR_WIDTH); + goto err; } - return 0; -} - -static int __init -plain_hash(void) -{ - char buf[PLAIN_BUF_SIZE]; - int ret; - - ret = plain_hash_to_buffer(PTR, buf, PLAIN_BUF_SIZE); - if (ret) - return ret; - - if (strncmp(buf, PTR_STR, PTR_WIDTH) == 0) - return -1; - - return 0; -} - -/* - * We can't use test() to test %p because we don't know what output to expect - * after an address is hashed. - */ -static void __init -plain(void) -{ - int err; + nchars = snprintf(hash, sizeof(hash), fmt, p); + if (nchars != PTR_WIDTH) { + pr_warn("vsprintf(\"%s\", p) returned number of characters %d, expected %d\n", + fmt, nchars, PTR_WIDTH); + goto err; + } - err = plain_hash(); - if (err) { - pr_warn("plain 'p' does not appear to be hashed\n"); - failed_tests++; + if (strncmp(hash, PTR_VAL_NO_CRNG, PTR_WIDTH) == 0) { + pr_warn_once("crng possibly not yet initialized. vsprinf(\"%s\", p) printed \"%s\"", + fmt, hash); + total_tests--; return; } - err = plain_format(); - if (err) { - pr_warn("hashing plain 'p' has unexpected format\n"); - failed_tests++; + /* + * There is a small chance of a false negative on 32-bit systems + * when the hash is the same as the pointer value. + */ + if (strncmp(hash, real, PTR_WIDTH) == 0) { + pr_warn("vsprintf(\"%s\", p) returned %s, expected hashed pointer\n", + fmt, hash); + goto err; + } + +#if BITS_PER_LONG == 64 + if (strncmp(hash, ZEROS, PTR_WIDTH / 2) != 0) { + pr_warn("vsprintf(\"%s\", p) returned %s, expected %s in the top half bits\n", + fmt, hash, ZEROS); + goto err; } +#endif + return; + +err: + failed_tests++; } static void __init -test_hashed(const char *fmt, const void *p) +plain(void) { - char buf[PLAIN_BUF_SIZE]; - int ret; - - /* - * No need to increase failed test counter since this is assumed - * to be called after plain(). - */ - ret = plain_hash_to_buffer(p, buf, PLAIN_BUF_SIZE); - if (ret) - return; - - test(buf, fmt, p); + test_hashed("%p", PTR); } static void __init -- 2.16.4