From patchwork Tue Feb 28 04:01:18 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexei Starovoitov X-Patchwork-Id: 13154394 X-Patchwork-Delegate: bpf@iogearbox.net 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 5DD51C64EC7 for ; Tue, 28 Feb 2023 04:02:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229752AbjB1ECC (ORCPT ); Mon, 27 Feb 2023 23:02:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60082 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229755AbjB1EBe (ORCPT ); Mon, 27 Feb 2023 23:01:34 -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 187961D939; Mon, 27 Feb 2023 20:01:34 -0800 (PST) Received: by mail-pg1-x52b.google.com with SMTP id d10so4843481pgt.12; Mon, 27 Feb 2023 20:01:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=xfIRyGkmgsSIXqW49jVysIDhg/kNcphUShFloi/6CTE=; b=PrF3pC2f7aWFl3e/qwvdaJGi61TIsJdNrfLRrSknqWMpwLydCcvpSiw979KxFakipN uIRWTQlLaosv9z+i7pwpr6fBaoL/3do86lYa3hoAUihAT9mUkUhGVL/3jW5jVAGkvr3Z iRGesTIFKnd0J3MUuIL5HkpYm88pcUujWG33rBlSvWb7SEArR6af/amv0KY2W0VxnYET 0EmrrGzCU0ye97MmplniNbwG7V8dmXO+wgOhtwfnmptNyxKJLXgQGEWTqd3mlbdJBKqf qiAE9Wnp+HVjLn4FKUes237jT0O+Sb1KZrpe6xi8IkQrDutfqo8cO8gm3j+ag5QbJDAk q4XA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=xfIRyGkmgsSIXqW49jVysIDhg/kNcphUShFloi/6CTE=; b=wt1wBbaIvRoFj0v/5QWCPZVPlrTI8JM+Lx79n7SgJ0kwQvvQWS07QQxESEdkZ1nNxf mRuWZbFhpdwgpdGlNEIsOXb9/fhglTOBdwHU5WJ6bEDN2/eiJXngj8Rf96vvvQLh5yOT mhQ4RQuarrbGLS+xipEyePjVWobvb9FFKGEdeFd7lcKNY6n2QfsLSPK1qxqOT7QWBh1U CnDTy9Nj/rGWuO+uwz3zw0QdNNpj2OJKs+qrYTQTNGVMabC2bqPMbm25KEuzNXuaUA41 rGknFMZF3Vhs32llUTieb/XKWS8kFc3PRSLnmbIbhIsCzZhX6Sn187fXRQxEb1mvdKF9 yZfA== X-Gm-Message-State: AO0yUKXsIUS9a7NHJFxAGX+okoG8wlE+yMFUuM/T0V2X/F8shMKa7Xhz rsCwcdN11Fz4sKnbE4ih78g= X-Google-Smtp-Source: AK7set8Z0Fr9C3HxQzjh25uGBdYNkOsPCzSklJQ8MAniTqy0pe+uK6cOORk3eVm7tVgYEIO00ZEjRQ== X-Received: by 2002:a62:5281:0:b0:5a8:4bfb:6bee with SMTP id g123-20020a625281000000b005a84bfb6beemr1135391pfb.9.1677556893515; Mon, 27 Feb 2023 20:01:33 -0800 (PST) Received: from macbook-pro-6.dhcp.thefacebook.com ([2620:10d:c090:400::5:6245]) by smtp.gmail.com with ESMTPSA id t6-20020aa79386000000b005907716bf8bsm4974917pfe.60.2023.02.27.20.01.31 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 27 Feb 2023 20:01:33 -0800 (PST) From: Alexei Starovoitov To: davem@davemloft.net Cc: daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org, void@manifault.com, davemarchevsky@meta.com, tj@kernel.org, memxor@gmail.com, netdev@vger.kernel.org, bpf@vger.kernel.org, kernel-team@fb.com Subject: [PATCH v3 bpf-next 2/5] bpf: Mark cgroups and dfl_cgrp fields as trusted. Date: Mon, 27 Feb 2023 20:01:18 -0800 Message-Id: <20230228040121.94253-3-alexei.starovoitov@gmail.com> X-Mailer: git-send-email 2.37.1 (Apple Git-137.1) In-Reply-To: <20230228040121.94253-1-alexei.starovoitov@gmail.com> References: <20230228040121.94253-1-alexei.starovoitov@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net 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 Acked-by: Tejun Heo --- kernel/bpf/verifier.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 5cb8b623f639..e4234266e76d 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5011,6 +5011,10 @@ static int bpf_map_direct_read(struct bpf_map *map, int off, int size, u64 *val) BTF_TYPE_SAFE_NESTED(struct task_struct) { const cpumask_t *cpus_ptr; + struct css_set *cgroups; +}; +BTF_TYPE_SAFE_NESTED(struct css_set) { + struct cgroup *dfl_cgrp; }; static bool nested_ptr_is_trusted(struct bpf_verifier_env *env, @@ -5022,6 +5026,7 @@ static bool nested_ptr_is_trusted(struct bpf_verifier_env *env, return false; BTF_TYPE_EMIT(BTF_TYPE_SAFE_NESTED(struct task_struct)); + BTF_TYPE_EMIT(BTF_TYPE_SAFE_NESTED(struct css_set)); return btf_nested_type_is_trusted(&env->log, reg, off); }