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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 806A7C55178 for ; Thu, 29 Oct 2020 09:00:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 142C320780 for ; Thu, 29 Oct 2020 09:00:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="qhQ4YkyV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726166AbgJ2I6l (ORCPT ); Thu, 29 Oct 2020 04:58:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41608 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725991AbgJ2I4w (ORCPT ); Thu, 29 Oct 2020 04:56:52 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9EDB0C0613D2; Thu, 29 Oct 2020 01:56:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=zoaWQCaukT2MSre+YOCy8lPWvGILO48toajhUZfqRO8=; b=qhQ4YkyVtUdCF+9/SxF+KkMnE/ D3OoH/RsujOjBjImJs3j7wsc+18+EhiCdslrW+7UAfcF/3Lpk99bGShz5x8vvO7NhRDvD/3/jIF/U sxjKHuC9kaCmjIQSe39nGdSprah7mG+Z3Qat31XoyHOzlVqjf1/QS7I84ZB/yiztmTbIZ9tig9v0X f2yLG+zhB53m3eNdAToBlpu4RWg/tOhEL5fYpqSM8QjSZe/Ra+mMDoJYV20tgz1OUmmI9HvfC/hqJ Iucc/rIbeuYDkc44YiTbpdM2F7LW26KSdHCYp3Ov/mUwi9UI3WMsbmPjsLva53P4rrTMzDSlxoDzk s6zrIsQQ==; Received: from hch by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kY3jh-0006wc-3k; Thu, 29 Oct 2020 08:56:45 +0000 Date: Thu, 29 Oct 2020 08:56:44 +0000 From: Christoph Hellwig To: Daniel Vetter Cc: DRI Development , LKML , kvm@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org, linux-s390@vger.kernel.org, Daniel Vetter , Jason Gunthorpe , Kees Cook , Dan Williams , Andrew Morton , John Hubbard , J??r??me Glisse , Jan Kara Subject: Re: [PATCH v4 08/15] mm: Add unsafe_follow_pfn Message-ID: <20201029085644.GA25658@infradead.org> References: <20201026105818.2585306-1-daniel.vetter@ffwll.ch> <20201026105818.2585306-9-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201026105818.2585306-9-daniel.vetter@ffwll.ch> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org > +int unsafe_follow_pfn(struct vm_area_struct *vma, unsigned long address, > + unsigned long *pfn) The one tab indent here looks weird, normally tis would be two tabs or aligned aftetthe opening brace. > +{ > +#ifdef CONFIG_STRICT_FOLLOW_PFN > + pr_info("unsafe follow_pfn usage rejected, see CONFIG_STRICT_FOLLOW_PFN\n"); > + return -EINVAL; > +#else > + WARN_ONCE(1, "unsafe follow_pfn usage\n"); > + add_taint(TAINT_USER, LOCKDEP_STILL_OK); > + > + return follow_pfn(vma, address, pfn); > +#endif Woudn't this be a pretty good use case of "if (IS_ENABLED(...)))"? Also I'd expect the inverse polarity of the config option, that is a USAFE_FOLLOW_PFN option to enable to unsafe behavior. > +/** > + * unsafe_follow_pfn - look up PFN at a user virtual address > + * @vma: memory mapping > + * @address: user virtual address > + * @pfn: location to store found PFN > + * > + * Only IO mappings and raw PFN mappings are allowed. > + * > + * Returns zero and the pfn at @pfn on success, -ve otherwise. > + */ > +int unsafe_follow_pfn(struct vm_area_struct *vma, unsigned long address, > + unsigned long *pfn) > +{ > + return follow_pfn(vma, address, pfn); > +} > +EXPORT_SYMBOL(unsafe_follow_pfn); Any reason this doesn't use the warn and disable logic?