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=-5.8 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 98056C433ED for ; Tue, 13 Apr 2021 07:39:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6DA406135C for ; Tue, 13 Apr 2021 07:39:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230441AbhDMHjl (ORCPT ); Tue, 13 Apr 2021 03:39:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53504 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229819AbhDMHjk (ORCPT ); Tue, 13 Apr 2021 03:39:40 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2D365C061574 for ; Tue, 13 Apr 2021 00:39:20 -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=qiMozfse1ylK7l2xDfgLoNIFT6bNFBlMbrxg4GooV1s=; b=UD2Y8PFbs0xVNGOqw1H3pLJCRv wM10LfvBbRL/39M1Tyjp+W5Q+mR5BNpFWb7KXu6tZm+tnHEvSyk0C5w0fJtwR/UskSnCusTB3e0NU EMP9ZcmBl6xwdPN9iT/s3Y6oZjklp4ypiOiure0d6oRT+SbRL4iavkFCy7q0G4+fLDo+uK/Bv5+Hn UIo+fN58zb4+E01+fySJsDy2qxFujCk3xmTbkEIri1+0HZ7I0paj26LBh+HHZcz5eaAuGlhrDT0H+ XrotGzlHsbobL1ruJrjlTHn3+1bFMRI4Eb8ET0Sg2x/EGHSq1wHxZcqV4tHjVCXFJLjxetbZpAetf MwHSazIA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94 #2 (Red Hat Linux)) id 1lWDb7-005PuV-Hl; Tue, 13 Apr 2021 07:37:00 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 5B71A30022D; Tue, 13 Apr 2021 09:36:32 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 2DA2920224209; Tue, 13 Apr 2021 09:36:32 +0200 (CEST) Date: Tue, 13 Apr 2021 09:36:32 +0200 From: Peter Zijlstra To: Kees Cook Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, boris.ostrovsky@oracle.com, jgross@suse.com, sstabellini@kernel.org, x86@kernel.org, jani.nikula@linux.intel.com, joonas.lahtinen@linux.intel.com, rodrigo.vivi@intel.com, chris@chris-wilson.co.uk, intel-gfx@lists.freedesktop.org, linux-mm@kvack.org, hch@lst.de Subject: Re: [PATCH 4/7] mm: Introduce verify_page_range() Message-ID: References: <20210412080012.357146277@infradead.org> <20210412080611.769864829@infradead.org> <202104121302.57D7EF8@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202104121302.57D7EF8@keescook> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 12, 2021 at 01:05:09PM -0700, Kees Cook wrote: > On Mon, Apr 12, 2021 at 10:00:16AM +0200, Peter Zijlstra wrote: > > +struct vpr_data { > > + int (*fn)(pte_t pte, unsigned long addr, void *data); > > + void *data; > > +}; > > Eeerg. This is likely to become an attack target itself. Stored function > pointer with stored (3rd) argument. > > This doesn't seem needed: only DRM uses it, and that's for error > reporting. I'd rather plumb back errors in a way to not have to add > another place in the kernel where we do func+arg stored calling. Is this any better? It does have the stored pointer, but not a stored argument, assuming you don't count returns as arguments I suppose. The alternative is refactoring apply_to_page_range() :-/ --- struct vpr_data { bool (*fn)(pte_t pte, unsigned long addr); unsigned long addr; }; static int vpr_fn(pte_t *pte, unsigned long addr, void *data) { struct vpr_data *vpr = data; if (!vpr->fn(*pte, addr)) { vpr->addr = addr; return -EINVAL; } return 0; } /** * verify_page_range() - Scan (and fill) a range of virtual memory and validate PTEs * @mm: mm identifying the virtual memory map * @addr: starting virtual address of the range * @size: size of the range * @fn: function that verifies the PTEs * * Scan a region of virtual memory, filling in page tables as necessary and * calling a provided function on each leaf, providing a copy of the * page-table-entry. * * Similar apply_to_page_range(), but does not provide direct access to the * page-tables. * * NOTE! this function does not work correctly vs large pages. * * Return: the address that failed verification or 0 on success. */ unsigned long verify_page_range(struct mm_struct *mm, unsigned long addr, unsigned long size, bool (*fn)(pte_t pte, unsigned long addr)) { struct vpr_data vpr = { .fn = fn, .addr = 0, }; apply_to_page_range(mm, addr, size, vpr_fn, &vpr); return vpr.addr; } EXPORT_SYMBOL_GPL(verify_page_range);