From patchwork Wed Jun 2 09:55:45 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Gleixner X-Patchwork-Id: 453192 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=-15.7 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, URIBL_BLOCKED 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 AF982C4708F for ; Wed, 2 Jun 2021 10:19:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 996AC613BF for ; Wed, 2 Jun 2021 10:19:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232971AbhFBKUy (ORCPT ); Wed, 2 Jun 2021 06:20:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37978 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232698AbhFBKUH (ORCPT ); Wed, 2 Jun 2021 06:20:07 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1CD56C061355; Wed, 2 Jun 2021 03:17:55 -0700 (PDT) Message-Id: <20210602101618.462908825@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1622629074; 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:content-transfer-encoding: references:references; bh=S+BtLMFUO8zq4x2FDJtHKocyWQSVYtuFhC95M+ZhZFc=; b=Ii3X8E/zAVy6/kZZ9z70Oi04k6dk1NnoNWKPvnlTeAeLsKtYbILctCzDWtCCwjyv2ElSz7 iWFbRpqAYaUn/PwT36EOssgMkrbtOjOyh8wkB6lo/ptXTpnd4uZtrmdZrTPrkdmbw61FNc RpZHYjhLglDgyUx5X2/AiL/BX9d/wKoWPuZSoeN06NoHW6Sb0fu9GEZpCcQ0c6MHEIlKdf 9gXbZuwbEBKpH9+bqafD+17SOm+obtFX1HETaT5RzonC5lEBd2iEF7egzNeF/bhlGsRqWN Mb1hrM8nQ/Js102htKHLmu33FSOokfHAg2VXooIes8OdXv+1F/PBe8pUwzq2cg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1622629074; 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:content-transfer-encoding: references:references; bh=S+BtLMFUO8zq4x2FDJtHKocyWQSVYtuFhC95M+ZhZFc=; b=pSq2Zv33pVpLNBaXnE7UDtDhnPcjAMqQcGuB+mn9IwV8t2qimSLm0nft1UbrWdDGujz3vu CgzO7/v4bW04/RCw== Date: Wed, 02 Jun 2021 11:55:45 +0200 From: Thomas Gleixner 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 2/8] x86/fpu: Prevent state corruption in __fpu__restore_sig() References: <20210602095543.149814064@linutronix.de> MIME-Version: 1.0 Content-transfer-encoding: 8-bit Precedence: bulk List-ID: X-Mailing-List: stable@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 --- arch/x86/include/asm/fpu/xstate.h | 4 ---- arch/x86/kernel/fpu/signal.c | 9 +-------- arch/x86/kernel/fpu/xstate.c | 2 +- 3 files changed, 2 insertions(+), 13 deletions(-) --- a/arch/x86/include/asm/fpu/xstate.h +++ b/arch/x86/include/asm/fpu/xstate.h @@ -112,8 +112,4 @@ void copy_supervisor_to_kernel(struct xr void copy_dynamic_supervisor_to_kernel(struct xregs_state *xstate, u64 mask); void copy_kernel_to_dynamic_supervisor(struct xregs_state *xstate, u64 mask); - -/* Validate an xstate header supplied by userspace (ptrace or sigreturn) */ -int validate_user_xstate_header(const struct xstate_header *hdr); - #endif --- 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; --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -515,7 +515,7 @@ int using_compacted_format(void) } /* Validate an xstate header supplied by userspace (ptrace or sigreturn) */ -int validate_user_xstate_header(const struct xstate_header *hdr) +static int validate_user_xstate_header(const struct xstate_header *hdr) { /* No unknown or supervisor features may be set */ if (hdr->xfeatures & ~xfeatures_mask_user())