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 EDB7FC6FA8E for ; Tue, 28 Feb 2023 16:46:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229674AbjB1QqD (ORCPT ); Tue, 28 Feb 2023 11:46:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37266 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229515AbjB1QqC (ORCPT ); Tue, 28 Feb 2023 11:46:02 -0500 Received: from mail-qv1-f52.google.com (mail-qv1-f52.google.com [209.85.219.52]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2316034C03; Tue, 28 Feb 2023 08:45:57 -0800 (PST) Received: by mail-qv1-f52.google.com with SMTP id nv15so7265796qvb.7; Tue, 28 Feb 2023 08:45:57 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=LYVO48FXas9roeOJnyiiq+0n+H4awkY5GZrrWNRYNF0=; b=2I4bxxqFbFu7q/PsAyTElTZR/eQQlYTjSeyXufZn0ub/sYCjQn0iRIXh8WX+KaaF3A vm1DyVb+Fn1gLU5XA2+Bm1ol/ee80xne4il2oAsutIN0NKO8q9uM3e61Yb5iQhTTtg0p DDto++3ue+bTJNPEKKGU8ndC1zAIlBzfcsj6icTaJlblmxaM1l4GSSU9+6cdeFRaBE6K m3Neg32+Vak6SXAkxydEhk/CGmlotU1DxBxldbXW0g/A4DQ2+Te61klHu65+UyuvDw8J 74CPRjCgWg9+VGp8x4NODhOztZJBvCTnXREbDeBsFFD7n+g/1kjSS7TNTtSXCjc7cMd4 HLUg== X-Gm-Message-State: AO0yUKXsQ7NExMRUtGB7SjKT8XM4y4QjeooDjeVrHalcfowtLI3McKgl s/0GYLHRV6vVku+D5qS6XkA= X-Google-Smtp-Source: AK7set+Hs0hpd1ZNKXTBvr7aHFo+ekwRQK23UYef40SCMeUIPBk/GIbSWc3wULRdW0oyhCoeTUVYTg== X-Received: by 2002:a05:6214:cad:b0:56b:f47b:1cd2 with SMTP id s13-20020a0562140cad00b0056bf47b1cd2mr7496153qvs.41.1677602756014; Tue, 28 Feb 2023 08:45:56 -0800 (PST) Received: from maniforge ([2620:10d:c091:480::1:f172]) by smtp.gmail.com with ESMTPSA id bl32-20020a05620a1aa000b007423e52f9d2sm7122602qkb.71.2023.02.28.08.45.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Feb 2023 08:45:55 -0800 (PST) Date: Tue, 28 Feb 2023 10:45:53 -0600 From: David Vernet To: Alexei Starovoitov Cc: davem@davemloft.net, daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org, davemarchevsky@meta.com, tj@kernel.org, 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> User-Agent: Mutt/2.2.9 (2022-11-12) 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 > 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: David Vernet