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=-19.1 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, 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 50242C49EC9 for ; Mon, 21 Jun 2021 16:48:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3BFDE610A3 for ; Mon, 21 Jun 2021 16:48:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231733AbhFUQuT (ORCPT ); Mon, 21 Jun 2021 12:50:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:38112 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231164AbhFUQrv (ORCPT ); Mon, 21 Jun 2021 12:47:51 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id BB9A86120D; Mon, 21 Jun 2021 16:33:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1624293225; bh=SLdZNVlc3QuvAH3Rngujdew2yvmtAj+wl+Hap5ihrjU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BXgS3yEJz/PtVIchon+65QdVQexEe3SchNmFxVrm48BDljZLp1hDHj+6q1MR2EBRh hG5qeO9WoNIE7APvElWFo8Wl7JwE3fxkkJKtMIhdQfZIdL6p59pXKLW7T/aFsb/kXn ViNzNXCtLzMXpV8IwcjTZ0dobs0XqfHoEFT6ZJbI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andy Lutomirski , Thomas Gleixner , Borislav Petkov , Dave Hansen , Rik van Riel Subject: [PATCH 5.12 145/178] x86/fpu: Invalidate FPU state after a failed XRSTOR from a user buffer Date: Mon, 21 Jun 2021 18:15:59 +0200 Message-Id: <20210621154927.708870613@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210621154921.212599475@linuxfoundation.org> References: <20210621154921.212599475@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Andy Lutomirski commit d8778e393afa421f1f117471144f8ce6deb6953a upstream. Both Intel and AMD consider it to be architecturally valid for XRSTOR to fail with #PF but nonetheless change the register state. The actual conditions under which this might occur are unclear [1], but it seems plausible that this might be triggered if one sibling thread unmaps a page and invalidates the shared TLB while another sibling thread is executing XRSTOR on the page in question. __fpu__restore_sig() can execute XRSTOR while the hardware registers are preserved on behalf of a different victim task (using the fpu_fpregs_owner_ctx mechanism), and, in theory, XRSTOR could fail but modify the registers. If this happens, then there is a window in which __fpu__restore_sig() could schedule out and the victim task could schedule back in without reloading its own FPU registers. This would result in part of the FPU state that __fpu__restore_sig() was attempting to load leaking into the victim task's user-visible state. Invalidate preserved FPU registers on XRSTOR failure to prevent this situation from corrupting any state. [1] Frequent readers of the errata lists might imagine "complex microarchitectural conditions". Fixes: 1d731e731c4c ("x86/fpu: Add a fastpath to __fpu__restore_sig()") Signed-off-by: Andy Lutomirski Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov Acked-by: Dave Hansen Acked-by: Rik van Riel Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20210608144345.758116583@linutronix.de Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/fpu/signal.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) --- a/arch/x86/kernel/fpu/signal.c +++ b/arch/x86/kernel/fpu/signal.c @@ -369,6 +369,25 @@ static int __fpu__restore_sig(void __use fpregs_unlock(); return 0; } + + /* + * The above did an FPU restore operation, restricted to + * the user portion of the registers, and failed, but the + * microcode might have modified the FPU registers + * nevertheless. + * + * If the FPU registers do not belong to current, then + * invalidate the FPU register state otherwise the task might + * preempt current and return to user space with corrupted + * FPU registers. + * + * In case current owns the FPU registers then no further + * action is required. The fixup below will handle it + * correctly. + */ + if (test_thread_flag(TIF_NEED_FPU_LOAD)) + __cpu_invalidate_fpregs_state(); + fpregs_unlock(); } else { /*