From patchwork Mon Jul 12 06:12:06 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 474485 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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, 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 C22C6C11F80 for ; Mon, 12 Jul 2021 06:28:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AF073610A6 for ; Mon, 12 Jul 2021 06:28:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234469AbhGLGbP (ORCPT ); Mon, 12 Jul 2021 02:31:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:52800 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237009AbhGLGab (ORCPT ); Mon, 12 Jul 2021 02:30:31 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9E5A2601FC; Mon, 12 Jul 2021 06:27:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626071263; bh=nEukOyTbLhZZ9KDODgLCPj+m5m81RFSNtNnCsHQf0PM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TOqxLLCfRQHE7+h5E+1QoEfBdCieOXyUyKk2PjnNsRdJvjbUAo6k7kgF7Uh+RcBWn KO/+txK4oRbwQFGunl0dYTcrrFIjSHXn7YeuKSKCVf3bCsvWltVCeKzP+gUQRqU+D/ g9OIHD8oIOUmApcyz7Cj9yYL9IgcRrsk+T9t9Um8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dave Hansen , Thomas Gleixner , "Aneesh Kumar K.V" , Ram Pai , Sandipan Das , Florian Weimer , "Desnes A. Nunes do Rosario" , Ingo Molnar , Thiago Jung Bauermann , Michael Ellerman , Michal Hocko , Michal Suchanek , Shuah Khan , Andrew Morton , Linus Torvalds , Sasha Levin Subject: [PATCH 5.4 342/348] selftests/vm/pkeys: fix alloc_random_pkey() to make it really, really random Date: Mon, 12 Jul 2021 08:12:06 +0200 Message-Id: <20210712060749.480520738@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210712060659.886176320@linuxfoundation.org> References: <20210712060659.886176320@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Dave Hansen [ Upstream commit f36ef407628835a7d7fb3d235b1f1aac7022d9a3 ] Patch series "selftests/vm/pkeys: Bug fixes and a new test". There has been a lot of activity on the x86 front around the XSAVE architecture which is used to context-switch processor state (among other things). In addition, AMD has recently joined the protection keys club by adding processor support for PKU. The AMD implementation helped uncover a kernel bug around the PKRU "init state", which actually applied to Intel's implementation but was just harder to hit. This series adds a test which is expected to help find this class of bug both on AMD and Intel. All the work around pkeys on x86 also uncovered a few bugs in the selftest. This patch (of 4): The "random" pkey allocation code currently does the good old: srand((unsigned int)time(NULL)); *But*, it unfortunately does this on every random pkey allocation. There may be thousands of these a second. time() has a one second resolution. So, each time alloc_random_pkey() is called, the PRNG is *RESET* to time(). This is nasty. Normally, if you do: srand(); foo = rand(); bar = rand(); You'll be quite guaranteed that 'foo' and 'bar' are different. But, if you do: srand(1); foo = rand(); srand(1); bar = rand(); You are quite guaranteed that 'foo' and 'bar' are the *SAME*. The recent "fix" effectively forced the test case to use the same "random" pkey for the whole test, unless the test run crossed a second boundary. Only run srand() once at program startup. This explains some very odd and persistent test failures I've been seeing. Link: https://lkml.kernel.org/r/20210611164153.91B76FB8@viggo.jf.intel.com Link: https://lkml.kernel.org/r/20210611164155.192D00FF@viggo.jf.intel.com Fixes: 6e373263ce07 ("selftests/vm/pkeys: fix alloc_random_pkey() to make it really random") Signed-off-by: Dave Hansen Signed-off-by: Thomas Gleixner Tested-by: Aneesh Kumar K.V Cc: Ram Pai Cc: Sandipan Das Cc: Florian Weimer Cc: "Desnes A. Nunes do Rosario" Cc: Ingo Molnar Cc: Thiago Jung Bauermann Cc: Michael Ellerman Cc: Michal Hocko Cc: Michal Suchanek Cc: Shuah Khan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- tools/testing/selftests/x86/protection_keys.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/x86/protection_keys.c b/tools/testing/selftests/x86/protection_keys.c index 47191af46617..a3602148e2ea 100644 --- a/tools/testing/selftests/x86/protection_keys.c +++ b/tools/testing/selftests/x86/protection_keys.c @@ -613,7 +613,6 @@ int alloc_random_pkey(void) int nr_alloced = 0; int random_index; memset(alloced_pkeys, 0, sizeof(alloced_pkeys)); - srand((unsigned int)time(NULL)); /* allocate every possible key and make a note of which ones we got */ max_nr_pkey_allocs = NR_PKEYS; @@ -1479,6 +1478,8 @@ int main(void) { int nr_iterations = 22; + srand((unsigned int)time(NULL)); + setup_handlers(); printf("has pku: %d\n", cpu_has_pku());