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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 2B1D5C47082 for ; Mon, 7 Jun 2021 08:49:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1256960E08 for ; Mon, 7 Jun 2021 08:49:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230368AbhFGIvB (ORCPT ); Mon, 7 Jun 2021 04:51:01 -0400 Received: from mail.skyhub.de ([5.9.137.197]:39728 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230311AbhFGIvA (ORCPT ); Mon, 7 Jun 2021 04:51:00 -0400 Received: from zn.tnic (p200300ec2f0b4f006e4c94f9871f2fda.dip0.t-ipconnect.de [IPv6:2003:ec:2f0b:4f00:6e4c:94f9:871f:2fda]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id A99E71EC0301; Mon, 7 Jun 2021 10:49:07 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1623055747; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=rdLasSxegzkWiQ/LEYu/db+S6HGIdzjYwkuMrqrwDFg=; b=cSCr2ZEYgb+YBeu8EI7Huew00jgvgLkeM68zlb2AxZ3dxb91r6wX5rUCD9DS7glplxopZI R9f8ptvi2Sgovedq/L6fEOmihHmCYYLtp+vFdHc6aScsqhigx5y95yD1nfLSds7JuuH8Uf 4WgKwy2lA18MeE4PVmLga09Sh/YHO5Q= Date: Mon, 7 Jun 2021 10:49:02 +0200 From: Borislav Petkov To: Thomas Gleixner Cc: LKML , x86@kernel.org, Andy Lutomirski , Dave Hansen , Fenghua Yu , Tony Luck , Yu-cheng Yu , Sebastian Andrzej Siewior , syzbot+2067e764dbcd10721e2e@syzkaller.appspotmail.com, stable@vger.kernel.org Subject: Re: [patch V2 02/14] x86/fpu: Prevent state corruption in __fpu__restore_sig() Message-ID: References: <20210605234742.712464974@linutronix.de> <20210606001323.067157324@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210606001323.067157324@linutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jun 06, 2021 at 01:47:44AM +0200, Thomas Gleixner wrote: > From: Thomas Gleixner > > The non-compacted slowpath uses __copy_from_user() and copies the entire > user buffer into the kernel buffer, verbatim. This means that the kernel > buffer may now contain entirely invalid state on which XRSTOR will #GP. > validate_user_xstate_header() can detect some of that corruption, but that > leaves the onus on callers to clear the buffer. > > Prior to XSAVES support it was possible just to reinitialize the buffer, > completely, but with supervisor states that is not longer possible as the > buffer clearing code split got it backwards. Fixing that is possible, but > not corrupting the state in the first place is more robust. > > Avoid corruption of the kernel XSAVE buffer by using copy_user_to_xstate() > which validates the XSAVE header contents before copying the actual states > to the kernel. copy_user_to_xstate() was previously only called for > compacted-format kernel buffers, but it works for both compacted and > non-compacted forms. > > Using it for the non-compacted form is slower because of multiple > __copy_from_user() operations, but that cost is less important than robust > code in an already slow path. > > [ Changelog polished by Dave Hansen ] > > Fixes: b860eb8dce59 ("x86/fpu/xstate: Define new functions for clearing fpregs and xstates") > Reported-by: syzbot+2067e764dbcd10721e2e@syzkaller.appspotmail.com > Signed-off-by: Thomas Gleixner > Cc: stable@vger.kernel.org > --- > V2: Removed the make validate_user_xstate_header() static hunks (Borislav) > --- > arch/x86/kernel/fpu/signal.c | 9 +-------- > 1 file changed, 1 insertion(+), 8 deletions(-) Very nice. Reviewed-by: Borislav Petkov -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette