From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C48C934BA5A; Thu, 26 Mar 2026 19:42:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774554127; cv=none; b=uzl18tYPPcKGHyHzEcRpabzvbO7qh/rGO0qXXwyGf/aGG9qDoE5d5C517iEYw5oOkPZjuvN4Z4E7p/YU+0zSLjkkhEqGzaGnoi6qe6U7HAjcgMB2eFK8sCyY07aiS8S73Aa0UsrHYutd7tDHbBidPOL/cxkpUj80iwfxB1xOCaI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774554127; c=relaxed/simple; bh=2c0nPF3JcBZBuucJxsAUZUSdm1t3EasoLZEnpiiV6GI=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=o1YzO4y6k/rH5Z6elH/O+LtNq9vsi3Rxrl9CSCodh4QdXcawoC3eAj0A3TcIrksZj8ds3VhDtPkvJ3zmLSqWw00vZRDh3hPAjcPcZWEUTK+bq5dhj1yMcTubfTK4FonMiMeJBQ2u1i/U2CssKsR7z94yuzqIwP6P4sBktbb8Uas= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Z2+AIPKx; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Z2+AIPKx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 648C6C116C6; Thu, 26 Mar 2026 19:42:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774554127; bh=2c0nPF3JcBZBuucJxsAUZUSdm1t3EasoLZEnpiiV6GI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Z2+AIPKxhFJSmMevO5N+1hoPO2EsnUrs8aLgabfyPdBD+QAAHosy/hnFPG8eL1yZn lCeKD1AhktlKKHTM105xkMd2JPEM8w3Vs3zm5MHOswPMXpb+mnFAN11hdkzMbwloQv Stm7AV6g6IycJBtilbKqwQ34mRN+CVdnFU5J2s9A7a2WwR7HFhridzOlBbVO1FUdN8 Ch6lK4Hxk/Pu9wA5Ed2O1F4V6yop8rNfgbYd4mPJAHZO8IbeOjtlAmFU4Isn72yhKq cvjzGg58LDdBymtZRnsNARPcYqsUtWZHvnvTpOIprp/QVZx05NsbIffwI/yYVJYk/6 OzBBv2fmKOcpg== Date: Thu, 26 Mar 2026 12:42:05 -0700 From: Jakub Kicinski To: Leon Hwang Cc: bpf@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shuah Khan , "David S . Miller" , Jesper Dangaard Brouer , Toke Hoiland-Jorgensen , Lorenzo Bianconi , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, netdev@vger.kernel.org, kernel-patches-bot@fb.com Subject: Re: [PATCH bpf-next 1/3] bpf: Disallow freplace on XDP with mismatched xdp_has_frags values Message-ID: <20260326124205.1a3bb825@kernel.org> In-Reply-To: <20260324150444.68166-2-leon.hwang@linux.dev> References: <20260324150444.68166-1-leon.hwang@linux.dev> <20260324150444.68166-2-leon.hwang@linux.dev> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 24 Mar 2026 23:04:42 +0800 Leon Hwang wrote: > The commit f45d5b6ce2e8 ("bpf: generalise tail call map compatibility check") > was to ensure backwards compatibility against tail calls. However, it > missed that XDP progs can be extended by freplace progs, which could break > the backwards compatibility, e.g. xdp_has_frags=true freplace progs are > allowed to attach to xdp_has_frags=false XDP progs. > > To avoid breaking the backwards compatibility via freplace, disallow > freplace on XDP programs with different xdp_has_frags values. It may be worth adding a selftest to tools/testing/selftests/drivers/net/xdp.py which sets MTU to 9k, tries to attach a non-frag-capable prog if that fails attaches a frag-capable prog and then checks if replacing the capable prog with non-capable fails. Drivers may be buggy in this regard.