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 E545DC6FA8E for ; Tue, 28 Feb 2023 19:39:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229874AbjB1Tjg (ORCPT ); Tue, 28 Feb 2023 14:39:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40842 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229671AbjB1Tjf (ORCPT ); Tue, 28 Feb 2023 14:39:35 -0500 Received: from mail-pg1-x52b.google.com (mail-pg1-x52b.google.com [IPv6:2607:f8b0:4864:20::52b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F01DF34F66; Tue, 28 Feb 2023 11:39:22 -0800 (PST) Received: by mail-pg1-x52b.google.com with SMTP id z10so6353781pgr.8; Tue, 28 Feb 2023 11:39:22 -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=opeBF3pAbytFzHeDJjyX+93c1jspBN+cmhhKcJuerEE=; b=e0zvJrjyAu0NnN7Ohm4W1bUswGWfzjBMpdNamloGQ/1mkvhKODmj76Kjg6o0gy8EyK ZhkIK0mEprcWVRcDpF2GNxLs8jX/0O8UZ3XY4hxAKQujLQa4VJiCFwJhv0z0AoJ1eIsj 3kJ9dW5JjjcL1Z+A9Onn9aF7ZSrl7ejc4vrCC4aVSPdofKku+crISEVIr20e6TS3wI6T OCyDhqLpPJz7zieaLdGpogPLuyvm5Ze7w+OjJg4eD5uLX9GoP/pijarMoPFj7X+/aSwW Z1Cc2KMWlIdkQy9flR2YfXkKeZi7OedV3FjxVwLMtFtFYZKGJTdVIRxc5s7LmgkbxLDm 3DCw== 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=opeBF3pAbytFzHeDJjyX+93c1jspBN+cmhhKcJuerEE=; b=MPN86Ufdc78ivf+5xP1YQ7WFl+PJp8YuImpJObc9i/D+8Rzf7Cf22ODsKlkGcOPMym /oI63ve9VPEHFfMfDTnTxEDgCBqByQUX39/1MpTIf6ksIcauHRl8J5jSHWI/RQhtQg3I RO3B6v7V7O1HhhMxdBa1wc+3/4Y9jwbrxK/3e2Yp91PdARVtTGVud9dHxiEu5s+Hh47X Y4qjtFQuk1JhzaagLrkRa24//w7XuvOFZWd7uQwXAVCQAglAVjAEUk7q4mTGil65R6lq wAVRFDBlT1KGQcP/EvHHKOxo07aHMy8b9J03UTaoG1f53EnJ9RSQ8yyxgUQwczDC85Ou MmSA== X-Gm-Message-State: AO0yUKWf/ZMN1CVjXLqw5ibgjbT2QXdJpDkip7XoMNjZZs3OXLUI+fnX p2t6kDo3W6hT5Znx9rUclx0= X-Google-Smtp-Source: AK7set9LLme16wQkBqHA50rGtrtm6cKUt/dNxstpNq0bUKqja7YYOtfNf8FGWsOnwHNMo++ZarEZlg== X-Received: by 2002:aa7:9607:0:b0:5e0:c59f:b008 with SMTP id q7-20020aa79607000000b005e0c59fb008mr1125733pfg.4.1677613162234; Tue, 28 Feb 2023 11:39:22 -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 u1-20020aa78381000000b005cd81a74821sm6369156pfm.152.2023.02.28.11.39.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Feb 2023 11:39:21 -0800 (PST) Sender: Tejun Heo Date: Tue, 28 Feb 2023 09:39:19 -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 3/5] bpf: Introduce kptr_rcu. Message-ID: References: <20230228040121.94253-1-alexei.starovoitov@gmail.com> <20230228040121.94253-4-alexei.starovoitov@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230228040121.94253-4-alexei.starovoitov@gmail.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, Feb 27, 2023 at 08:01:19PM -0800, Alexei Starovoitov wrote: > From: Alexei Starovoitov > > The life time of certain kernel structures like 'struct cgroup' is protected by RCU. > Hence it's safe to dereference them directly from __kptr tagged pointers in bpf maps. > The resulting pointer is MEM_RCU and can be passed to kfuncs that expect KF_RCU. > Derefrence of other kptr-s returns PTR_UNTRUSTED. > > For example: > struct map_value { > struct cgroup __kptr *cgrp; > }; > > SEC("tp_btf/cgroup_mkdir") > int BPF_PROG(test_cgrp_get_ancestors, struct cgroup *cgrp_arg, const char *path) > { > struct cgroup *cg, *cg2; > > cg = bpf_cgroup_acquire(cgrp_arg); // cg is PTR_TRUSTED and ref_obj_id > 0 > bpf_kptr_xchg(&v->cgrp, cg); > > cg2 = v->cgrp; // This is new feature introduced by this patch. > // cg2 is PTR_MAYBE_NULL | MEM_RCU. > // When cg2 != NULL, it's a valid cgroup, but its percpu_ref could be zero > > bpf_cgroup_ancestor(cg2, level); // safe to do. > } > > Signed-off-by: Alexei Starovoitov >From cgroup POV: Acked-by: Tejun Heo Thanks. -- tejun