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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 44B44C74A5B for ; Wed, 29 Mar 2023 17:14:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231304AbjC2ROe (ORCPT ); Wed, 29 Mar 2023 13:14:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39224 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231252AbjC2ROd (ORCPT ); Wed, 29 Mar 2023 13:14:33 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2A2CD5FDB for ; Wed, 29 Mar 2023 10:13:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1680110023; 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=2HKY/Ux5TNZKEBOMV/tb21I2tofWYzDVBz54QvkxgBg=; b=F1feGtSTlDKeQTzUsbxQ2+jphGbKaNs1PxPofPSS6S0g3jnchv+wDGn0AewTOL/Kyu5zby Da2DoSHk2Auxp8ZezeTRbTNC66Cobhl7BAa8Jicx5CDiomGZXBAgy0G85SEeth4rnhFgpN qTaiXyAAIw2TZEP0QESAokOPoAfxkYU= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-93-wDlX7MaCPTeV1v8QlV9ksg-1; Wed, 29 Mar 2023 13:13:36 -0400 X-MC-Unique: wDlX7MaCPTeV1v8QlV9ksg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4B37485A588; Wed, 29 Mar 2023 17:13:35 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.224.161]) by smtp.corp.redhat.com (Postfix) with SMTP id 32E7F4020C82; Wed, 29 Mar 2023 17:13:30 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 29 Mar 2023 19:13:27 +0200 (CEST) Date: Wed, 29 Mar 2023 19:13:22 +0200 From: Oleg Nesterov To: Gregory Price Cc: Arnd Bergmann , Gregory Price , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Linux-Arch , avagin@gmail.com, Peter Zijlstra , Andy Lutomirski , krisman@collabora.com, Thomas Gleixner , Jonathan Corbet , shuah , Catalin Marinas , Will Deacon , Mark Rutland , tongtiangen@huawei.com, Robin Murphy Subject: Re: [PATCH v14 1/4] asm-generic,arm64: create task variant of access_ok Message-ID: <20230329171322.GB4477@redhat.com> References: <20230328164811.2451-1-gregory.price@memverge.com> <20230328164811.2451-2-gregory.price@memverge.com> <20230329151515.GA913@redhat.com> <9a456346-e207-44e1-873e-40d21334e01b@app.fastmail.com> <20230329160322.GA4477@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 03/28, Gregory Price wrote: > > Not sure how I should proceed here, Can't we just kill this access_ok() in set_syscall_user_dispatch() ? I don't think it buys too much. Oleg. diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c index 0b6379adff6b..d2e516ece52b 100644 --- a/kernel/entry/syscall_user_dispatch.c +++ b/kernel/entry/syscall_user_dispatch.c @@ -43,11 +43,7 @@ bool syscall_user_dispatch(struct pt_regs *regs) return false; if (likely(sd->selector)) { - /* - * access_ok() is performed once, at prctl time, when - * the selector is loaded by userspace. - */ - if (unlikely(__get_user(state, sd->selector))) { + if (unlikely(get_user(state, sd->selector))) { force_exit_sig(SIGSEGV); return true; } @@ -86,9 +82,6 @@ int set_syscall_user_dispatch(unsigned long mode, unsigned long offset, if (offset && offset + len <= offset) return -EINVAL; - if (selector && !access_ok(selector, sizeof(*selector))) - return -EFAULT; - break; default: return -EINVAL;