From patchwork Fri Mar 26 16:05:00 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lorenz Bauer X-Patchwork-Id: 410533 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0BFEBC433E1 for ; Fri, 26 Mar 2021 16:06:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D8D2461A36 for ; Fri, 26 Mar 2021 16:06:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230272AbhCZQGL (ORCPT ); Fri, 26 Mar 2021 12:06:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44432 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230266AbhCZQFm (ORCPT ); Fri, 26 Mar 2021 12:05:42 -0400 Received: from mail-wr1-x42d.google.com (mail-wr1-x42d.google.com [IPv6:2a00:1450:4864:20::42d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EE035C0613AA for ; Fri, 26 Mar 2021 09:05:41 -0700 (PDT) Received: by mail-wr1-x42d.google.com with SMTP id j7so6179565wrd.1 for ; Fri, 26 Mar 2021 09:05:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloudflare.com; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=zQoMkVCtgJGZXmdu3KME93w0y7DWMF1NiaK0WZ/Njao=; b=c+9PKPHPQWy3wo5EWypLaXKArM+ciNIfHE9FYOFvc0BOz5q9EWn7yxqrFQQCXvrx7L TRTWIsmNz/YnqEJpjoTDkww998W9jGgrXntAcm0BwD/WFpYONRR0yox8H0w3KCM8pkbX aTDw/tcCgAq/eDw9tVYDqEp0GY1JInboUh670= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=zQoMkVCtgJGZXmdu3KME93w0y7DWMF1NiaK0WZ/Njao=; b=No+nAJ3qg1idPQjbm7VMb/tL30vrwURhMmNz2njjSIGQtzu0pjXyTnx4ZPtTNGt/Qr tD5RQ6+jpchKZF4TyKUDw2g3ut/jkBmCvvbHqlVwC/5lvgcAmiP+f0eXRufHj69m8ozg w+P+rDPxbXu1eJBNxM64o13fVrqmrzLSpueiJVrTHw8HLgbNJx8kJNT5fD/BaktjWVi2 oIerYcLESIzrXlqJVARYRLRWwbP3odgaccRotSHOqo3SE+Rq0maKfZ+3FM2ucnwzN/gR dwrduC6bY6FpPjDu3rXq04UB4DKuXFw+gNwlCdc7CJkxK+1d8dfYaJkaWzL1QSppHhx9 OSrQ== X-Gm-Message-State: AOAM532Zi3OwE9+ltameOznQGpW3YXTIlvGiZhj2B44zw2V7cu0I+Fo8 wVwcSldVXqdHdAhM/Wruma4xKw== X-Google-Smtp-Source: ABdhPJxcmgrtuRv8romzbSyTFqTQSEJa4We5oSZ52yZtkB8W2HhNmi/u9IhtgCmLrgu5W1J+ucGIvQ== X-Received: by 2002:a5d:4582:: with SMTP id p2mr14928666wrq.34.1616774740745; Fri, 26 Mar 2021 09:05:40 -0700 (PDT) Received: from localhost.localdomain (5.0.8.c.b.e.d.6.4.e.c.a.1.e.f.4.f.f.6.2.a.5.a.7.0.b.8.0.1.0.0.2.ip6.arpa. [2001:8b0:7a5a:26ff:4fe1:ace4:6deb:c805]) by smtp.gmail.com with ESMTPSA id s20sm11692879wmj.36.2021.03.26.09.05.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Mar 2021 09:05:40 -0700 (PDT) From: Lorenz Bauer To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org Cc: kernel-team@cloudflare.com, netdev@vger.kernel.org, bpf@vger.kernel.org, Lorenz Bauer Subject: [PATCH bpf v2 1/2] bpf: link: refuse non-O_RDWR flags in BPF_OBJ_GET Date: Fri, 26 Mar 2021 16:05:00 +0000 Message-Id: <20210326160501.46234-1-lmb@cloudflare.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Invoking BPF_OBJ_GET on a pinned bpf_link checks the path access permissions based on file_flags, but the returned fd ignores flags. This means that any user can acquire a "read-write" fd for a pinned link with mode 0664 by invoking BPF_OBJ_GET with BPF_F_RDONLY in file_flags. The fd can be used to invoke BPF_LINK_DETACH, etc. Fix this by refusing non-O_RDWR flags in BPF_OBJ_GET. This works because OBJ_GET by default returns a read write mapping and libbpf doesn't expose a way to override this behaviour for programs and links. Fixes: 70ed506c3bbc ("bpf: Introduce pinnable bpf_link abstraction") Signed-off-by: Lorenz Bauer Acked-by: Andrii Nakryiko --- kernel/bpf/inode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c index 1576ff331ee4..dc56237d6960 100644 --- a/kernel/bpf/inode.c +++ b/kernel/bpf/inode.c @@ -547,7 +547,7 @@ int bpf_obj_get_user(const char __user *pathname, int flags) else if (type == BPF_TYPE_MAP) ret = bpf_map_new_fd(raw, f_flags); else if (type == BPF_TYPE_LINK) - ret = bpf_link_new_fd(raw); + ret = (f_flags != O_RDWR) ? -EINVAL : bpf_link_new_fd(raw); else return -ENOENT;