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=-11.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS 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 29483C43387 for ; Tue, 8 Jan 2019 13:02:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E97B12087F for ; Tue, 8 Jan 2019 13:01:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1546952520; bh=1GUtVawmR1rZ/xbQBj/ApQdCkLNOqKcJO4g+GCNXuCQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=tRr3gnQ/JvWC/SeEKc6nz23AO9YF4+Eaup5zndK9/SkfAkvpDhLbjqROu4aY+IA4v xbbiz2MPV1dg5HN2nAtLgxgD6XaVoeccXhB4F735PU1WZWhhqGUvak+IlhBf44Zlad xKXI65X7nUFd/uwZu4J7dRTEkvlHyifc839qZB3g= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727780AbfAHNB7 (ORCPT ); Tue, 8 Jan 2019 08:01:59 -0500 Received: from casper.infradead.org ([85.118.1.10]:49728 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727558AbfAHNB7 (ORCPT ); Tue, 8 Jan 2019 08:01:59 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:Content-Type: MIME-Version:References:In-Reply-To:Message-ID:Subject:Cc:To:From:Date:Sender :Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=bVwU6K5HlEtnhIB7t0fPUsILlFg9pdVy5AAR5gFiRoo=; b=hybly7lq97XhAjAHnkOcpigjkQ /2PkyTkMYKwWdVauZsAsxFcgR1lfSFGrt5iKnRJcOHxgKTRHeGWb/QLLS7I9+5jKCp0GWcM8UfbE7 Jlj0D6FchOxyMaayPIBFhVoEEe9hrVfT3hMFo6KrRw+WiA/uwJUQXmcCC9P2X6Tw3OzUbUWSSluSe V8DBj+3qrwltEdRQDz756IhE4Wd06AOjfCoAmmIucFklqys8Vki2poWgl0JZr551T+uzYNm0lds1b S163ed7BAm2op+N3Oh6V+WqsB06CZJ4TOMJ5XYqCkldQqz4Xl5Yxtb/bQN7JoT5rywU27FqCwIGFQ 5cT9fI7w==; Received: from 177.41.113.230.dynamic.adsl.gvt.net.br ([177.41.113.230] helo=coco.lan) by casper.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1ggr13-0002sD-2M; Tue, 08 Jan 2019 13:01:57 +0000 Date: Tue, 8 Jan 2019 11:01:53 -0200 From: Mauro Carvalho Chehab To: Sakari Ailus Cc: linux-media@vger.kernel.org, hverkuil@xs4all.nl, laurent.pinchart@ideasonboard.com Subject: Re: [PATCH v2 1/3] videobuf2-core: Prevent size alignment wrapping buffer size to 0 Message-ID: <20190108110153.7582a4a0@coco.lan> In-Reply-To: <20190108105955.68009949@coco.lan> References: <20190108085836.9376-1-sakari.ailus@linux.intel.com> <20190108085836.9376-2-sakari.ailus@linux.intel.com> <20190108105212.66837b9a@coco.lan> <20190108105955.68009949@coco.lan> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Em Tue, 8 Jan 2019 10:59:55 -0200 Mauro Carvalho Chehab escreveu: > Em Tue, 8 Jan 2019 10:52:12 -0200 > Mauro Carvalho Chehab escreveu: > > > Em Tue, 8 Jan 2019 10:58:34 +0200 > > Sakari Ailus escreveu: > > > > > PAGE_ALIGN() may wrap the buffer size around to 0. Prevent this by > > > checking that the aligned value is not smaller than the unaligned one. > > > > > > Note on backporting to stable: the file used to be under > > > drivers/media/v4l2-core, it was moved to the current location after 4.14. > > > > > > Signed-off-by: Sakari Ailus > > > Cc: stable@vger.kernel.org > > > Reviewed-by: Hans Verkuil > > > --- > > > drivers/media/common/videobuf2/videobuf2-core.c | 4 ++++ > > > 1 file changed, 4 insertions(+) > > > > > > diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c > > > index 0ca81d495bda..0234ddbfa4de 100644 > > > --- a/drivers/media/common/videobuf2/videobuf2-core.c > > > +++ b/drivers/media/common/videobuf2/videobuf2-core.c > > > @@ -207,6 +207,10 @@ static int __vb2_buf_mem_alloc(struct vb2_buffer *vb) > > > for (plane = 0; plane < vb->num_planes; ++plane) { > > > unsigned long size = PAGE_ALIGN(vb->planes[plane].length); > > > > > > + /* Did it wrap around? */ > > > + if (size < vb->planes[plane].length) > > > + goto free; > > > + > > > > Sorry, but I can't see how this could ever happen (except for a very serious > > bug at the compiler or at the hardware). > > > > See, the definition at PAGE_ALIGN is (from mm.h): > > > > #define PAGE_ALIGN(addr) ALIGN(addr, PAGE_SIZE) > > > > and the macro it uses come from kernel.h: > > > > #define __ALIGN_KERNEL(x, a) __ALIGN_KERNEL_MASK(x, (typeof(x))(a) - 1) > > #define __ALIGN_KERNEL_MASK(x, mask) (((x) + (mask)) & ~(mask)) > > .. > > #define ALIGN(x, a) __ALIGN_KERNEL((x), (a)) > > > > So, this: > > size = PAGE_ALIGN(length); > > > > (assuming PAGE_SIZE= 0x1000) > > > > becomes: > > > > size = (length + 0x0fff) & ~0xfff; > > > > so, size will *always* be >= length. > > Hmm... after looking at patch 2, now I understand what's your concern... > > If someone indeed uses length = INT_MAX, size will indeed be zero. In time, I meant to say UINT_MAX. > > Please adjust the description accordingly, as it doesn't reflect > that. > > Btw, in this particular case, I would use a WARN_ON(), as this is > something that indicates not only a driver bug (as the driver is > letting someone to request a buffer a way too big), but probably > also an attempt from a hacker to try to crack the system. > > Thanks, > Mauro Thanks, Mauro