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 49360C64ED6 for ; Tue, 28 Feb 2023 19:32:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229806AbjB1Tcs (ORCPT ); Tue, 28 Feb 2023 14:32:48 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34826 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229884AbjB1Tcp (ORCPT ); Tue, 28 Feb 2023 14:32:45 -0500 Received: from mail-pf1-x436.google.com (mail-pf1-x436.google.com [IPv6:2607:f8b0:4864:20::436]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B735733474; Tue, 28 Feb 2023 11:32:41 -0800 (PST) Received: by mail-pf1-x436.google.com with SMTP id u20so6493321pfm.7; Tue, 28 Feb 2023 11:32:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date:message-id :reply-to; bh=O2L0ttHm+/TkRLQEPj0BgPCqHHA0WUnIL4IMzbCPwzE=; b=Iy8qB9Z1kMtM1MTX1VPnLNaFlrUc6GdkaN7+FaqLbVBAshZeC5lMkinzk9jp/i+4xV /0HIJghk4Z6ToOZa/my9BRFaxtaxBNWqpq9EPOsnwjI5D2XErj8gPuQzIBaByeJk/pZc HIh+8jJFGSGKcoMqon8vyVGX+n+0i5pLmoXktRoPm4Lx8tDBfPCV8W7mCuDsbwuT0nH1 I2ZFICe3Axgto7u6Pk9uGMA4uUkTTN+Bh0l92pTX9MyESZR08kwH+XRwPs5DqlzAUy5Z ve3P2nIin6zzUcTVv9FaERrJbone9EzXD/im6+a5B1v2rx0PrdQ+RIu7ZJzqck45UvAX ZQLQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=O2L0ttHm+/TkRLQEPj0BgPCqHHA0WUnIL4IMzbCPwzE=; b=wKL2wLdFP68fOKSylVVrISDvzXP2xq85Ylfl6VANg4VgP/ze/Ug3EtP35oO70n7ATc lpe0HpcyR6ele2M0RONp49u2ulwov7jLTBC8nGfRu1KUxOmsum3koIu+7bFm5IDH2yu2 n3NIUR/OLO4fk2wtKLYihL1U46y2Z4psKKK+NpiV/gMYh1tOfI2UJCsTGCMzSKrziWsM SjALZ7o4ULPhjAm+8mEnaR9MPqtq5cJBF0oNiU6iGb2hagzsGobfBDcP0yIa0az6PM8Z YujpB9/w8vPSOmB5/8x6ARwLS5AYJKXXRyp8k1rSb9dpgH4M9LpLO5zwUO17dublSpFA XuOQ== X-Gm-Message-State: AO0yUKUM8xrUMrPXdJjaDQ3w+3vOyQfzD71gBhgSOTShRknsdgL70R3G GBkqvu7zmendSMw5GhGwcaI= X-Google-Smtp-Source: AK7set/NsBZzMwC2RvLZxEARHzT6MyElSzKxy1pIoxxyboLy/+ZTqbG9OrK5Zqf1B7ZEGWlp4iYhsg== X-Received: by 2002:a62:79c5:0:b0:593:befd:848c with SMTP id u188-20020a6279c5000000b00593befd848cmr4419327pfc.16.1677612760805; Tue, 28 Feb 2023 11:32:40 -0800 (PST) Received: from localhost (2603-800c-1a02-1bae-a7fa-157f-969a-4cde.res6.spectrum.com. [2603:800c:1a02:1bae:a7fa:157f:969a:4cde]) by smtp.gmail.com with ESMTPSA id c9-20020a637249000000b00502f20aa4desm6076987pgn.70.2023.02.28.11.32.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Feb 2023 11:32:39 -0800 (PST) Sender: Tejun Heo Date: Tue, 28 Feb 2023 09:32:38 -1000 From: Tejun Heo To: Alexei Starovoitov Cc: davem@davemloft.net, daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org, void@manifault.com, davemarchevsky@meta.com, memxor@gmail.com, netdev@vger.kernel.org, bpf@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH v3 bpf-next 2/5] bpf: Mark cgroups and dfl_cgrp fields as trusted. Message-ID: References: <20230228040121.94253-1-alexei.starovoitov@gmail.com> <20230228040121.94253-3-alexei.starovoitov@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230228040121.94253-3-alexei.starovoitov@gmail.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, Feb 27, 2023 at 08:01:18PM -0800, Alexei Starovoitov wrote: > From: Alexei Starovoitov > > bpf programs sometimes do: > bpf_cgrp_storage_get(&map, task->cgroups->dfl_cgrp, ...); > It is safe to do, because cgroups->dfl_cgrp pointer is set diring init and ^ u > never changes. The task->cgroups is also never NULL. It is also set during init > and will change when task switches cgroups. For any trusted task pointer > dereference of cgroups and dfl_cgrp should yield trusted pointers. The verifier > wasn't aware of this. Hence in gcc compiled kernels task->cgroups dereference > was producing PTR_TO_BTF_ID without modifiers while in clang compiled kernels > the verifier recognizes __rcu tag in cgroups field and produces > PTR_TO_BTF_ID | MEM_RCU | MAYBE_NULL. > Tag cgroups and dfl_cgrp as trusted to equalize clang and gcc behavior. > When GCC supports btf_type_tag such tagging will done directly in the type. > > Signed-off-by: Alexei Starovoitov Acked-by: Tejun Heo Thanks. -- tejun