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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 37B05C76186 for ; Wed, 24 Jul 2019 02:43:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 138D220828 for ; Wed, 24 Jul 2019 02:43:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726296AbfGXCn3 (ORCPT ); Tue, 23 Jul 2019 22:43:29 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54790 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725372AbfGXCn2 (ORCPT ); Tue, 23 Jul 2019 22:43:28 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 340F7308212D; Wed, 24 Jul 2019 02:43:28 +0000 (UTC) Received: from treble (ovpn-120-73.rdu2.redhat.com [10.10.120.73]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BA48D601B7; Wed, 24 Jul 2019 02:43:26 +0000 (UTC) Date: Tue, 23 Jul 2019 21:43:24 -0500 From: Josh Poimboeuf To: Thomas Gleixner Cc: LKML , Nick Desaulniers , Nathan Chancellor , clang-built-linux , x86@kernel.org, Arnd Bergmann , Sedat Dilek , Peter Zijlstra , Linus Torvalds Subject: Re: x86 - clang / objtool status Message-ID: <20190724023946.yxsz5im22fz4zxrn@treble> References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Wed, 24 Jul 2019 02:43:28 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 18, 2019 at 10:40:09PM +0200, Thomas Gleixner wrote: > drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x86: redundant UACCESS disable Looking at this one, I think I agree with objtool. PeterZ, Linus, I know y'all discussed this code a few months ago. __copy_from_user() already does a CLAC in its error path. So isn't the user_access_end() redundant for the __copy_from_user() error path? Untested fix: diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c index 5fae0e50aad0..41dab9ea33cd 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c @@ -1628,6 +1628,7 @@ static int check_relocations(const struct drm_i915_gem_exec_object2 *entry) static int eb_copy_relocations(const struct i915_execbuffer *eb) { + struct drm_i915_gem_relocation_entry *relocs; const unsigned int count = eb->buffer_count; unsigned int i; int err; @@ -1635,7 +1636,6 @@ static int eb_copy_relocations(const struct i915_execbuffer *eb) for (i = 0; i < count; i++) { const unsigned int nreloc = eb->exec[i].relocation_count; struct drm_i915_gem_relocation_entry __user *urelocs; - struct drm_i915_gem_relocation_entry *relocs; unsigned long size; unsigned long copied; @@ -1663,14 +1663,8 @@ static int eb_copy_relocations(const struct i915_execbuffer *eb) if (__copy_from_user((char *)relocs + copied, (char __user *)urelocs + copied, - len)) { -end_user: - user_access_end(); -end: - kvfree(relocs); - err = -EFAULT; - goto err; - } + len)) + goto end; copied += len; } while (copied < size); @@ -1699,10 +1693,14 @@ static int eb_copy_relocations(const struct i915_execbuffer *eb) return 0; +end_user: + user_access_end(); +end: + kvfree(relocs); + err = -EFAULT; err: while (i--) { - struct drm_i915_gem_relocation_entry *relocs = - u64_to_ptr(typeof(*relocs), eb->exec[i].relocs_ptr); + relocs = u64_to_ptr(typeof(*relocs), eb->exec[i].relocs_ptr); if (eb->exec[i].relocation_count) kvfree(relocs); }