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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,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 225F2C3A5A5 for ; Tue, 3 Sep 2019 04:51:48 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9748721881 for ; Tue, 3 Sep 2019 04:51:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=neuling.org header.i=@neuling.org header.b="JFiE14M8" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9748721881 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=neuling.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 46MvgN5gz5zDqfL for ; Tue, 3 Sep 2019 14:51:44 +1000 (AEST) Received: from ozlabs.org (bilbo.ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 46Mvb81466zDqf5 for ; Tue, 3 Sep 2019 14:48:04 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=neuling.org Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=neuling.org header.i=@neuling.org header.b="JFiE14M8"; dkim-atps=neutral Received: from neuling.org (localhost [127.0.0.1]) by ozlabs.org (Postfix) with ESMTP id 46Mvb742wvz9sN1; Tue, 3 Sep 2019 14:48:03 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=neuling.org; s=201811; t=1567486083; bh=56O+kCXt/bx3nXkVVp8ufeGXi+N1KOnytsXbuWp6W4c=; h=From:To:Cc:Subject:Date:From; b=JFiE14M8bt2kgjbx6DLIyghabJwdjSJpIZsdkIGfyrTL/gT8uPg7AUTJqPggZsMbp RUDVh7biWis/LhW6EcTLgz2INHhV+orc75wdO710Gl8OM8MREuB3d9vuXpdbXAbWNM f09ErCraw/uEpRKxHKgLori+RyvZGU7o6xbixlhyeMHV9ZxZF1IVgFct0cAZV6BFxK JA4hcT82d89eHpRXGC/ZjcMmVhqw9yExYuxnGGUNjz1KCD1JsLQjVkaibAjwHTytWX kRv0zdB/sZjkEO78+Aj+vDCTp8uclhoWRC6+deJUMTzW4MQQluhFdnadkZqBhFqhBv pHEJsK17RoSBg== Received: by neuling.org (Postfix, from userid 1000) id 81A772A581E; Tue, 3 Sep 2019 14:48:03 +1000 (AEST) From: Michael Neuling To: mpe@ellerman.id.au Subject: [PATCH 1/3] powerpc/tm: Fix FP/VMX unavailable exceptions inside a transaction Date: Tue, 3 Sep 2019 14:47:16 +1000 Message-Id: <20190903044718.13773-1-mikey@neuling.org> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, cyrilbur@gmail.com, Gustavo Romero Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: Gustavo Romero When we take an FP unavailable exception in a transaction we have to account for the hardware FP TM checkpointed registers being incorrect. In this case for this process we know the current and checkpointed FP registers must be the same (since FP wasn't used inside the transaction) hence in the thread_struct we copy the current FP registers to the checkpointed ones. This copy is done in tm_reclaim_thread(). We use thread->ckpt_regs.msr to determine if FP was on when in userspace. thread->ckpt_regs.msr represents the state of the MSR when exiting userspace. This is setup by check_if_tm_restore_required(). Unfortunatley there is an optimisation in giveup_all() which returns early if tsk->thread.regs->msr (via local variable `usermsr`) has FP=VEC=VSX=SPE=0. This optimisation means that check_if_tm_restore_required() is not called and hence thread->ckpt_regs.msr is not updated and will contain an old value. This can happen if due to load_fp=255 we start a userspace process with MSR FP=1 and then we are context switched out. In this case thread->ckpt_regs.msr will contain FP=1. If that same process is then context switched in and load_fp overflows, MSR will have FP=0. If that process now enters a transaction and does an FP instruction, the FP unavailable will not update thread->ckpt_regs.msr (the bug) and MSR FP=1 will be retained in thread->ckpt_regs.msr. tm_reclaim_thread() will then not perform the required memcpy and the checkpointed FP regs in the thread struct will contain the wrong values. The code path for this happening is: Userspace: Kernel Start userspace with MSR FP/VEC/VSX/SPE=0 TM=1 < ----- ... tbegin bne fp instruction FP unavailable ---- > fp_unavailable_tm() tm_reclaim_current() tm_reclaim_thread() giveup_all() return early since FP/VMX/VSX=0 /* ckpt MSR not updated (Incorrect) */ tm_reclaim() /* thread_struct ckpt FP regs contain junk (OK) */ /* Sees ckpt MSR FP=1 (Incorrect) */ no memcpy() performed /* thread_struct ckpt FP regs not fixed (Incorrect) */ tm_recheckpoint() /* Put junk in hardware checkpoint FP regs */ .... < ----- Return to userspace with MSR TM=1 FP=1 with junk in the FP TM checkpoint TM rollback reads FP junk This is a data integrity problem for the current process as the FP registers are corrupted. It's also a security problem as the FP registers from one process may be leaked to another. This patch moves up check_if_tm_restore_required() in giveup_all() to ensure thread->ckpt_regs.msr is updated correctly. A simple testcase to replicate this will be posted to tools/testing/selftests/powerpc/tm/tm-poison.c Similarly for VMX. This fixes CVE-2019-15030. Fixes: f48e91e87e67 ("powerpc/tm: Fix FP and VMX register corruption") Cc: stable@vger.kernel.org # 4.12+ Signed-off-by: Gustavo Romero Signed-off-by: Michael Neuling --- arch/powerpc/kernel/process.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 8fc4de0d22..437b57068c 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -497,13 +497,14 @@ void giveup_all(struct task_struct *tsk) if (!tsk->thread.regs) return; + check_if_tm_restore_required(tsk); + usermsr = tsk->thread.regs->msr; if ((usermsr & msr_all_available) == 0) return; msr_check_and_set(msr_all_available); - check_if_tm_restore_required(tsk); WARN_ON((usermsr & MSR_VSX) && !((usermsr & MSR_FP) && (usermsr & MSR_VEC))); -- 2.21.0