From patchwork Thu May 7 16:49:04 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu-cheng Yu X-Patchwork-Id: 226311 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=-14.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 DBCBEC38A24 for ; Thu, 7 May 2020 16:50:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B0C5E20870 for ; Thu, 7 May 2020 16:50:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726712AbgEGQuR (ORCPT ); Thu, 7 May 2020 12:50:17 -0400 Received: from mga05.intel.com ([192.55.52.43]:43277 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726531AbgEGQuR (ORCPT ); Thu, 7 May 2020 12:50:17 -0400 IronPort-SDR: cjuoT0SQTDfVqtbMxVZtA6VW+kuCC5BTXiedrIY5+HBRKrWgjXX2LjCfCU8nXrrzQX1/OtyB1n +KgXicC7yeag== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 May 2020 09:50:15 -0700 IronPort-SDR: Ms9q1mkGk1TD+317CGrZFl70J8ycy1T6V+H20BPKVdBhqKbvUSeZXJw6f8cRlz8hi3C9iRTiZ9 RLGaVuVla6MA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,364,1583222400"; d="scan'208";a="461910078" Received: from yyu32-desk.sc.intel.com ([143.183.136.146]) by fmsmga005.fm.intel.com with ESMTP; 07 May 2020 09:50:15 -0700 From: Yu-cheng Yu To: linux-kernel@vger.kernel.org, x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , Dave Hansen , Tony Luck , Andy Lutomirski , Borislav Petkov , Rik van Riel , "Ravi V. Shankar" , Sebastian Andrzej Siewior , Fenghua Yu , Peter Zijlstra Cc: Yu-cheng Yu , sam , Kees Cook , Alexey Dobriyan , Dave Hansen , Jann Horn , Andrew Morton , Alexander Potapenko , Al Viro , stable@vger.kernel.org Subject: [PATCH] x86/fpu/xstate: Clear uninitialized xstate areas in core dump Date: Thu, 7 May 2020 09:49:04 -0700 Message-Id: <20200507164904.26927-1-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org In a core dump, copy_xstate_to_kernel() copies only enabled user xfeatures to a kernel buffer without touching areas for disabled xfeatures. However, those uninitialized areas may contain random data, which is then written to the core dump file and can be read by a non-privileged user. Fix it by clearing uninitialized areas. Link: https://github.com/google/kmsan/issues/76 Link: https://lore.kernel.org/lkml/20200419100848.63472-1-glider@google.com/ Signed-off-by: Yu-cheng Yu Reported-by: sam Cc: "H. Peter Anvin" Cc: Kees Cook Cc: Alexey Dobriyan Cc: Thomas Gleixner Cc: Dave Hansen Cc: Jann Horn Cc: Ingo Molnar Cc: Andrew Morton Cc: Borislav Petkov Cc: Alexander Potapenko Cc: Al Viro Cc: --- arch/x86/kernel/fpu/xstate.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 32b153d38748..0856daa29be7 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -983,6 +983,7 @@ int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int of { unsigned int offset, size; struct xstate_header header; + int last_off; int i; /* @@ -1006,7 +1007,17 @@ int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int of __copy_xstate_to_kernel(kbuf, &header, offset, size, size_total); + last_off = 0; + for (i = 0; i < XFEATURE_MAX; i++) { + /* + * Clear uninitialized area before XSAVE header. + */ + if (i == FIRST_EXTENDED_XFEATURE) { + memset(kbuf + last_off, 0, XSAVE_HDR_OFFSET - last_off); + last_off = XSAVE_HDR_OFFSET + XSAVE_HDR_SIZE; + } + /* * Copy only in-use xstates: */ @@ -1020,11 +1031,16 @@ int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int of if (offset + size > size_total) break; + memset(kbuf + last_off, 0, offset - last_off); + last_off = offset + size; + __copy_xstate_to_kernel(kbuf, src, offset, size, size_total); } } + memset(kbuf + last_off, 0, size_total - last_off); + if (xfeatures_mxcsr_quirk(header.xfeatures)) { offset = offsetof(struct fxregs_state, mxcsr); size = MXCSR_AND_FLAGS_SIZE;