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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_NEOMUTT 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 BE188C46460 for ; Wed, 29 May 2019 07:25:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A145D208CB for ; Wed, 29 May 2019 07:25:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726723AbfE2HZu convert rfc822-to-8bit (ORCPT ); Wed, 29 May 2019 03:25:50 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:52742 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725894AbfE2HZu (ORCPT ); Wed, 29 May 2019 03:25:50 -0400 Received: from bigeasy by Galois.linutronix.de with local (Exim 4.80) (envelope-from ) id 1hVsxw-0002SA-HC; Wed, 29 May 2019 09:25:40 +0200 Date: Wed, 29 May 2019 09:25:40 +0200 From: Sebastian Andrzej Siewior To: Andrew Morton Cc: Hugh Dickins , x86@kernel.org, Mike Rapoport , Andrea Arcangeli , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Borislav Petkov , Pavel Machek , Dave Hansen Subject: [PATCH v2] x86/fpu: Use fault_in_pages_writeable() for pre-faulting Message-ID: <20190529072540.g46j4kfeae37a3iu@linutronix.de> References: <20190526173325.lpt5qtg7c6rnbql5@linutronix.de> <20190528211826.0fa593de5f2c7480357d3ca5@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8BIT In-Reply-To: <20190528211826.0fa593de5f2c7480357d3ca5@linux-foundation.org> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Hugh Dickins Since commit d9c9ce34ed5c8 ("x86/fpu: Fault-in user stack if copy_fpstate_to_sigframe() fails") we use get_user_pages_unlocked() to pre-faulting user's memory if a write generates a pagefault while the handler is disabled. This works in general and uncovered a bug as reported by Mike Rapoport. It has been pointed out that this function may be fragile and a simple pre-fault as in fault_in_pages_writeable() would be a better solution. Better as in taste and simplicity: That write (as performed by the alternative function) performs exactly the same faulting of memory that we had before. This was suggested by Hugh Dickins and Andrew Morton. Use fault_in_pages_writeable() for pre-faulting of user's stack. Fixes: d9c9ce34ed5c8 ("x86/fpu: Fault-in user stack if copy_fpstate_to_sigframe() fails") Suggested-by: Andrew Morton Signed-off-by: Hugh Dickins [bigeasy: patch description] Signed-off-by: Sebastian Andrzej Siewior --- v1…v2: Added a Fixes tag. arch/x86/kernel/fpu/signal.c | 11 ++--------- 1 file changed, 2 insertions(+), 9 deletions(-) diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c index 5a8d118bc423e..060d6188b4533 100644 --- a/arch/x86/kernel/fpu/signal.c +++ b/arch/x86/kernel/fpu/signal.c @@ -5,6 +5,7 @@ #include #include +#include #include #include @@ -189,15 +190,7 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size) fpregs_unlock(); if (ret) { - int aligned_size; - int nr_pages; - - aligned_size = offset_in_page(buf_fx) + fpu_user_xstate_size; - nr_pages = DIV_ROUND_UP(aligned_size, PAGE_SIZE); - - ret = get_user_pages_unlocked((unsigned long)buf_fx, nr_pages, - NULL, FOLL_WRITE); - if (ret == nr_pages) + if (!fault_in_pages_writeable(buf_fx, fpu_user_xstate_size)) goto retry; return -EFAULT; } -- 2.20.1