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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 3660AC4332D for ; Fri, 20 Mar 2020 16:15:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0E8D120739 for ; Fri, 20 Mar 2020 16:15:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584720922; bh=dKpCjXh35N/OLn+Ga/h917LVkpQQKxH6YGvz9EUVQtY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=C7mho+8RDf0ogqPF3J0IGFXbcP5Jm+wdvhxSZEQSEBKZjDThT4VWFzE454ndGb21G 5cUNgN8wFo6iZet1Lo8K8ph+GQiU8jN9Cv2P+2VD9ZzlgvDU7FHVBZ9EIN2o6TEeA7 Sojw8VqdAn3ARyD15eGrnWLdXUB10FZHLBtMhu2Q= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727523AbgCTQPT (ORCPT ); Fri, 20 Mar 2020 12:15:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:48894 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726935AbgCTQPT (ORCPT ); Fri, 20 Mar 2020 12:15:19 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id ADA6420724; Fri, 20 Mar 2020 16:15:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584720918; bh=dKpCjXh35N/OLn+Ga/h917LVkpQQKxH6YGvz9EUVQtY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dpFWKqRo2BwfiVY3lnyH8On6ZhnfmfFbF81Ms4KFgH0sZCPO4V6FT++I8XSeFP9gV q+2VBwlJ+auupvJulJT8WHsmnk572sa7Z5ebg8gfLu9q6wPmI4Q0Et018B6a4PRTcG 1bwsNvris9qrtrySUz1JeZUxor7OvsEC60bHw8AY= Date: Fri, 20 Mar 2020 17:15:15 +0100 From: Greg Kroah-Hartman To: Daniel Borkmann Cc: Alexei Starovoitov , Martin KaFai Lau , Song Liu , Yonghong Song , Andrii Nakryiko , netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, Maciej =?utf-8?Q?=C5=BBenczykowski?= , John Stultz , Alexander Potapenko , Alistair Delva Subject: Re: [PATCH] bpf: explicitly memset the bpf_attr structure Message-ID: <20200320161515.GA778529@kroah.com> References: <20200320094813.GA421650@kroah.com> <3bcf52da-0930-a27f-60f9-28a40e639949@iogearbox.net> <20200320154518.GA765793@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Mar 20, 2020 at 05:04:24PM +0100, Daniel Borkmann wrote: > On 3/20/20 4:45 PM, Greg Kroah-Hartman wrote: > > On Fri, Mar 20, 2020 at 04:24:32PM +0100, Daniel Borkmann wrote: > > > On 3/20/20 10:48 AM, Greg Kroah-Hartman wrote: > > > > For the bpf syscall, we are relying on the compiler to properly zero out > > > > the bpf_attr union that we copy userspace data into. Unfortunately that > > > > doesn't always work properly, padding and other oddities might not be > > > > correctly zeroed, and in some tests odd things have been found when the > > > > stack is pre-initialized to other values. > > > > > > > > Fix this by explicitly memsetting the structure to 0 before using it. > > > > > > > > Reported-by: Maciej Żenczykowski > > > > Reported-by: John Stultz > > > > Reported-by: Alexander Potapenko > > > > Reported-by: Alistair Delva > > > > Cc: stable > > > > Link: https://android-review.googlesource.com/c/kernel/common/+/1235490 > > > > Signed-off-by: Greg Kroah-Hartman > > > > --- > > > > kernel/bpf/syscall.c | 3 ++- > > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > > > > index a91ad518c050..a4b1de8ea409 100644 > > > > --- a/kernel/bpf/syscall.c > > > > +++ b/kernel/bpf/syscall.c > > > > @@ -3354,7 +3354,7 @@ static int bpf_map_do_batch(const union bpf_attr *attr, > > > > SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size) > > > > { > > > > - union bpf_attr attr = {}; > > > > + union bpf_attr attr; > > > > int err; > > > > if (sysctl_unprivileged_bpf_disabled && !capable(CAP_SYS_ADMIN)) > > > > @@ -3366,6 +3366,7 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz > > > > size = min_t(u32, size, sizeof(attr)); > > > > /* copy attributes from user space, may be less than sizeof(bpf_attr) */ > > > > + memset(&attr, 0, sizeof(attr)); > > > > > > Thanks for the fix, there are a few more of these places. We would also need > > > to cover: > > > > > > - bpf_prog_get_info_by_fd() > > > > Unless I am mistaken, struct bpf_prog_info is packed fully, with no > > holes, so this shouldn't be an issue there. > > It does have a '/* XXX 31 bits hole, try to pack */' but I presume the compiler > might simply zero it in this case. > > > > - bpf_map_get_info_by_fd() > > > > No padding in struct bpf_map_info that I can see, so I doubt this is > > needed there. > > > > > - btf_get_info_by_fd() > > > > There is no padding in struct bpf_btf_info, so that's not needed there, > > but I can add it if you really want. > > > > I can change these, but I don't think that there currently is a bug in > > those functions, unlike with "union bpf_attr" which, as Yonghong points > > out, is tripping on the CHECK_ATTR() test later on. > > Got it, my main concern is that the next time someone extends these fields with > new members we could potentially add holes in there as well and we'll run into > the same issue twice, example from the past is b85fab0e67b1 ("bpf: Add gpl_compatible > flag to struct bpf_prog_info"). Fair enough, I'll make a second patch for this, as there's no known issue today with those initializations that need to be backported to the stable tree :) thanks, greg k-h