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 AD3DAC5479D for ; Thu, 5 Jan 2023 19:40:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235717AbjAETkr (ORCPT ); Thu, 5 Jan 2023 14:40:47 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38446 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236067AbjAETkV (ORCPT ); Thu, 5 Jan 2023 14:40:21 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E66A81DF0D; Thu, 5 Jan 2023 11:38:06 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id A01FEB8111F; Thu, 5 Jan 2023 19:38:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A8BCFC433EF; Thu, 5 Jan 2023 19:38:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1672947484; bh=KBdBzlc3g1iDGQnK6row4ab6NJe99uJpRoP/gxBZW28=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=YAKtTrpWtz7GX/i3gnravZDqno40s8qwhlWs/sCoVkRvfYMNu4YmgKOzVOlBbialJ GsicuuYOltbMgIhasLVbHL48gfQSkA0QxoWLNPlIKN6Fc7xog1pnO05IJjZ/3ANpd/ zF1QwdDtk9ZqLxfj9a9cyXI4/sibc3/vle5KvFHE= Date: Thu, 5 Jan 2023 20:38:01 +0100 From: Greg KH To: Kees Cook Cc: Jens Axboe , Pavel Begunkov , "Gustavo A. R. Silva" , stable@vger.kernel.org, io-uring@vger.kernel.org, Dylan Yudaken , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH] io_uring: Replace 0-length array with flexible array Message-ID: References: <20230105033743.never.628-kees@kernel.org> <202301051003.27CF3DC@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202301051003.27CF3DC@keescook> Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Thu, Jan 05, 2023 at 10:04:19AM -0800, Kees Cook wrote: > On Thu, Jan 05, 2023 at 08:39:48AM +0100, Greg KH wrote: > > On Wed, Jan 04, 2023 at 07:37:48PM -0800, Kees Cook wrote: > > > Zero-length arrays are deprecated[1]. Replace struct io_uring_buf_ring's > > > "bufs" with a flexible array member. (How is the size of this array > > > verified?) Detected with GCC 13, using -fstrict-flex-arrays=3: > > > > > > In function 'io_ring_buffer_select', > > > inlined from 'io_buffer_select' at io_uring/kbuf.c:183:10: > > > io_uring/kbuf.c:141:23: warning: array subscript 255 is outside the bounds of an interior zero-length array 'struct io_uring_buf[0]' [-Wzero-length-bounds] > > > 141 | buf = &br->bufs[head]; > > > | ^~~~~~~~~~~~~~~ > > > In file included from include/linux/io_uring.h:7, > > > from io_uring/kbuf.c:10: > > > include/uapi/linux/io_uring.h: In function 'io_buffer_select': > > > include/uapi/linux/io_uring.h:628:41: note: while referencing 'bufs' > > > 628 | struct io_uring_buf bufs[0]; > > > | ^~~~ > > > > > > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays > > > > > > Fixes: c7fb19428d67 ("io_uring: add support for ring mapped supplied buffers") > > > Cc: Jens Axboe > > > Cc: Pavel Begunkov > > > Cc: "Gustavo A. R. Silva" > > > Cc: stable@vger.kernel.org > > > > Build problem aside, why is this a stable kernel issue? > > My thinking was that since this is technically a UAPI change, it'd be > best to get it changed as widely as possible. You can't break the uapi, so it should be the same with or without your change right? confused, greg k-h