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,URIBL_BLOCKED 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 5AC57C47092 for ; Wed, 2 Jun 2021 15:58:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3110B61492 for ; Wed, 2 Jun 2021 15:58:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232531AbhFBP75 (ORCPT ); Wed, 2 Jun 2021 11:59:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59152 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231614AbhFBP74 (ORCPT ); Wed, 2 Jun 2021 11:59:56 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9F7F9C061574; Wed, 2 Jun 2021 08:58:13 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1622649492; 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: in-reply-to:in-reply-to:references:references; bh=WBUTfGNxNvSgHbeI2jsrGUtW90Hi09xpMn/ER3bz4aI=; b=Q1HwTSAnNmKjG5VfbJrVPl0BZWtHe38jyV+9UlcAlmzAPTv1hMSMJ/2x+pAdZrm8h2XLiT 7LFtuwAc1OXzxpcZiKKFr4fCJh8iFUuRZZV3dJBkvwrbuihHZG688gdgsF69czjqnZNpBY JyNMVZWiVP6xXCiOroqDBCPrN2uQqeKByOmKOt9fvAnjn26zzJmgQa4+JP9M/wjX1zRvCo oej198PKio4KyPds2VpNU8j021wiDJ3atzuBneAI9ISgpD2Y/0lHOsSxpCszq4s5hYLrRj OWi7hTI9dZqEZmcLKOcunI6XdT6rRrX1tpJceTQiVlE10f7OyBppl578PYm1zg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1622649492; 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: in-reply-to:in-reply-to:references:references; bh=WBUTfGNxNvSgHbeI2jsrGUtW90Hi09xpMn/ER3bz4aI=; b=xvTHoFzERmxU1F7J1o/5k/I5q454qdshhO0o5mjdMinO9NI1Zm8xG/UHbadWCvqQF9VMJz zCFIjOThBTxNewDg== To: LKML Cc: x86@kernel.org, Andy Lutomirski , Dave Hansen , Fenghua Yu , Tony Luck , Yu-cheng Yu , syzbot+2067e764dbcd10721e2e@syzkaller.appspotmail.com, stable@vger.kernel.org Subject: [patch V2 2/8] x86/fpu: Prevent state corruption in __fpu__restore_sig() In-Reply-To: <20210602101618.462908825@linutronix.de> References: <20210602095543.149814064@linutronix.de> <20210602101618.462908825@linutronix.de> Date: Wed, 02 Jun 2021 17:58:11 +0200 Message-ID: <87y2bsz2b0.ffs@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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(-) --- a/arch/x86/kernel/fpu/signal.c +++ b/arch/x86/kernel/fpu/signal.c @@ -405,14 +405,7 @@ static int __fpu__restore_sig(void __use if (use_xsave() && !fx_only) { u64 init_bv = xfeatures_mask_user() & ~user_xfeatures; - if (using_compacted_format()) { - ret = copy_user_to_xstate(&fpu->state.xsave, buf_fx); - } else { - ret = __copy_from_user(&fpu->state.xsave, buf_fx, state_size); - - if (!ret && state_size > offsetof(struct xregs_state, header)) - ret = validate_user_xstate_header(&fpu->state.xsave.header); - } + ret = copy_user_to_xstate(&fpu->state.xsave, buf_fx); if (ret) goto err_out;