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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 19777C433F5 for ; Thu, 14 Oct 2021 03:10:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EA1AB610D0 for ; Thu, 14 Oct 2021 03:10:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229882AbhJNDM4 (ORCPT ); Wed, 13 Oct 2021 23:12:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54896 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229496AbhJNDM4 (ORCPT ); Wed, 13 Oct 2021 23:12:56 -0400 Received: from mail-ot1-x32b.google.com (mail-ot1-x32b.google.com [IPv6:2607:f8b0:4864:20::32b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BCA64C061570; Wed, 13 Oct 2021 20:10:51 -0700 (PDT) Received: by mail-ot1-x32b.google.com with SMTP id d21-20020a9d4f15000000b0054e677e0ac5so6379147otl.11; Wed, 13 Oct 2021 20:10:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=MDcIaKQ5v9Uwb9iAdAtQgCdcI6fVMvMf7iMJVcoRZNY=; b=B429JZV/z6LMkDJeR+RpZcUWKQPrYn8GDkQB43bsVK1tDGeo4J5mNuitjQJyPQ0n8z jLw7zBn+h220gYYX7WP+Ydz6dEF9LqrVxt+rz4RMLnEouovd+3vImzRctMe1dmYlhVpq WtBTuwFjuP5p58EuVcphgqGc+bFVizQbTRiuXSYkXJtOes4uH6/j/UQcSltKqsPqPEB2 T1DTlR1gCLZfbKPESNy8KXJCdC4Ex4CXvNySjDGRlslIhDAoAATyK8H412m7mfSp8pNx oK80IgQ4XDkvEr4i7PwaJ9N1gfgLvqopXOvP4TN277XLp3mk2SncQqkoSBK3L0aU8J7Y gdag== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=MDcIaKQ5v9Uwb9iAdAtQgCdcI6fVMvMf7iMJVcoRZNY=; b=wuv2WnLuhOVIVORDEi2iD+9Vgk6QGH7wBoQOndjMxY3N4PM41H5Or3EdXaHVetH0Dn MBk+qG6UOPYrenFGb1d6lVjTKRT/3rnsTpn7v5a8qXD7M9ELQmfUI0UhX2RCyO5/HjIM jODBeAJgdfOBApAU37EikWwaO7WgQY6JiQJ4WLhTa9aCoL3J7pffX8iHJj5SDt7ESftj WlCMDBF80SiaP6wsJL6dRUaysVcD1aAJgXN+t3dDmSHUQIjC2Dn3cEQ+P4EUCM+xIWqQ VuIu6tLcLzHa6IzkHEgddZsugkyDCacK2XdLR5MejsTgZ5qTW57o82qTaC4rzJZe7Kq/ ydAQ== X-Gm-Message-State: AOAM531j4ludh7dZEczBGtP1j9hKTxc9HbH8EDhrMEn02cOIhOTkaUnj Vx0bq2vvDt95Uk5n+EmqkQxQp5ao8hVs9A== X-Google-Smtp-Source: ABdhPJzuRjsbUZY+gCV5v11n1amFzerZaVhz32/94M9+JjEqkPFuJWMAoVB+wNEvPHASX9/TgaB94A== X-Received: by 2002:a05:6830:35a:: with SMTP id h26mr307225ote.369.1634181051071; Wed, 13 Oct 2021 20:10:51 -0700 (PDT) Received: from Davids-MacBook-Pro.local ([8.48.134.40]) by smtp.googlemail.com with ESMTPSA id t5sm340740oic.4.2021.10.13.20.10.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 13 Oct 2021 20:10:50 -0700 (PDT) Subject: Re: [PATCH net-next 1/3] net, neigh: Add build-time assertion to avoid neigh->flags overflow To: Daniel Borkmann , davem@davemloft.net, kuba@kernel.org Cc: roopa@nvidia.com, dsahern@kernel.org, m@lambda.lt, john.fastabend@gmail.com, netdev@vger.kernel.org, bpf@vger.kernel.org References: <20211013132140.11143-1-daniel@iogearbox.net> <20211013132140.11143-2-daniel@iogearbox.net> From: David Ahern Message-ID: Date: Wed, 13 Oct 2021 21:10:49 -0600 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20211013132140.11143-2-daniel@iogearbox.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 10/13/21 7:21 AM, Daniel Borkmann wrote: > Currently, NDA_FLAGS_EXT flags allow a maximum of 24 bits to be used for > extended neighbor flags. These are eventually fed into neigh->flags by > shifting with NTF_EXT_SHIFT as per commit 2c611ad97a82 ("net, neigh: > Extend neigh->flags to 32 bit to allow for extensions"). > > If really ever needed in future, the full 32 bits from NDA_FLAGS_EXT can > be used, it would only require to move neigh->flags from u32 to u64 inside > the kernel. > > Add a build-time assertion such that when extending the NTF_EXT_MASK with > new bits, we'll trigger an error once we surpass the 24th bit. This assumes > that no bit holes in new NTF_EXT_* flags will slip in from UAPI, but I > think this is reasonable to assume. > > Suggested-by: David Ahern > Signed-off-by: Daniel Borkmann > --- > net/core/neighbour.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/net/core/neighbour.c b/net/core/neighbour.c > index eae73efa9245..4fc601f9cd06 100644 > --- a/net/core/neighbour.c > +++ b/net/core/neighbour.c > @@ -1940,6 +1940,9 @@ static int neigh_add(struct sk_buff *skb, struct nlmsghdr *nlh, > NL_SET_ERR_MSG(extack, "Invalid extended flags"); > goto out; > } > + BUILD_BUG_ON(sizeof(neigh->flags) * BITS_PER_BYTE < > + (sizeof(ndm->ndm_flags) * BITS_PER_BYTE + > + hweight32(NTF_EXT_MASK))); > ndm_flags |= (ext << NTF_EXT_SHIFT); > } > if (ndm->ndm_ifindex) { > Reviewed-by: David Ahern