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[23.128.96.18]) by mx.google.com with ESMTP id cx18si9698742edb.323.2020.06.09.11.31.14; Tue, 09 Jun 2020 11:31:37 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=DPikTQ6F; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389043AbgFIS03 (ORCPT + 99 others); Tue, 9 Jun 2020 14:26:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47002 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731916AbgFIS0W (ORCPT ); Tue, 9 Jun 2020 14:26:22 -0400 Received: from mail-lj1-x244.google.com (mail-lj1-x244.google.com [IPv6:2a00:1450:4864:20::244]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 92E94C05BD1E; Tue, 9 Jun 2020 11:26:22 -0700 (PDT) Received: by mail-lj1-x244.google.com with SMTP id 9so26330721ljc.8; Tue, 09 Jun 2020 11:26:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=/MS9Y1NckTNUGInM9fo7+yYKL81LHnuUrE4ZS9tUH7g=; b=DPikTQ6FcOWi2xrpQfnqWVvm6/TQuJuZJFq1dFpl6Dsv7SXbIyqsRgvVUAJHN8NA5/ 4ZyotKF7uRw/fJVAdAnhcCbJA25jOOBTWjeYI573uPiJI6ttNZl7ut6DC1w1p9TEqMQq bOGXtZi/nQZSFyigS4lXIBPyKoLA6OjZeRc28ZHnmWF22CygGrscBrirRXRuuDTjTF/E V5KdvyWhvA5i2CNmuPHF+3ftELR0FjhMqHjlAuCUCUEslu19dV5BAqDY7EhMBoQHwzo8 7mJf9AbGhHY4SKc//y9ymx5vDx0Lc7hke0nkuCD4C2QSOm/vaoXVNFxpa6otHPhncXfj LkeQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=/MS9Y1NckTNUGInM9fo7+yYKL81LHnuUrE4ZS9tUH7g=; b=CmDNspyxBDNGGedu4rcFcoJUE7VxYeG6VWenQwPSnk6AiCThSrR2MUZzQ49/+hLOht GPyh05tJhBvmHK3iRl/lADL/Ses+lB9EnTKhb/ooXmzdVegMsjzAfkDQCThihUGG1k5l EIvPyGnXqnsrDbY4flTxuMlwkVztEKeknNrxdkwm+7tuUXifFPivgm8VybbD2+Xfn0ny tLI5Lui2a9lKwYdbnoYv2x6NqTPCRiCk2vvACA6MxboWaAyUtbquCDLCyMy+g2TDJpxV IoPfRbC1u4PC0HLmfpnfdrErTw3oy8qjj08IwWNIHvUYB4wtPSB8bWByWPu6UmJQeJfB S+Kg== X-Gm-Message-State: AOAM530nHCIOsTqkv7h+xy0MBTEWLkXuTqgH/u3HfDi3MfZifq28nfix VfMehDf8iqcAtMFia4lMJWTIw1Yq/mptQr46JIM= X-Received: by 2002:a05:651c:1193:: with SMTP id w19mr14859026ljo.121.1591727181004; Tue, 09 Jun 2020 11:26:21 -0700 (PDT) MIME-Version: 1.0 References: <20200608162202.94002-1-lmb@cloudflare.com> In-Reply-To: <20200608162202.94002-1-lmb@cloudflare.com> From: Alexei Starovoitov Date: Tue, 9 Jun 2020 11:26:09 -0700 Message-ID: Subject: Re: [PATCH bpf] bpf: cgroup: allow multi-attach program to replace itself To: Lorenz Bauer Cc: Alexei Starovoitov , Daniel Borkmann , Shuah Khan , Andrii Nakryiko , Roman Gushchin , kernel-team , Network Development , bpf , LKML , "open list:KERNEL SELFTEST FRAMEWORK" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 8, 2020 at 9:22 AM Lorenz Bauer wrote: > > When using BPF_PROG_ATTACH to attach a program to a cgroup in > BPF_F_ALLOW_MULTI mode, it is not possible to replace a program > with itself. This is because the check for duplicate programs > doesn't take the replacement program into account. > > Replacing a program with itself might seem weird, but it has > some uses: first, it allows resetting the associated cgroup storage. > Second, it makes the API consistent with the non-ALLOW_MULTI usage, > where it is possible to replace a program with itself. Third, it > aligns BPF_PROG_ATTACH with bpf_link, where replacing itself is > also supported. > > Sice this code has been refactored a few times this change will > only apply to v5.7 and later. Adjustments could be made to > commit 1020c1f24a94 ("bpf: Simplify __cgroup_bpf_attach") and > commit d7bf2c10af05 ("bpf: allocate cgroup storage entries on attaching bpf programs") > as well as commit 324bda9e6c5a ("bpf: multi program support for cgroup+bpf") > > Signed-off-by: Lorenz Bauer > Fixes: af6eea57437a ("bpf: Implement bpf_link-based cgroup BPF program attachment") Applied. Thanks