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 X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 885FCC41603 for ; Mon, 12 Apr 2021 09:31:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7535B6120B for ; Mon, 12 Apr 2021 09:31:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242428AbhDLJ2d (ORCPT ); Mon, 12 Apr 2021 05:28:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:57432 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239993AbhDLJE0 (ORCPT ); Mon, 12 Apr 2021 05:04:26 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 95FEB61285; Mon, 12 Apr 2021 09:02:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1618218125; bh=dWSUi5Gfr9eYdzkPHZh9tRTFmME/SJI8qKg2Gp6MiDc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XDFF5skSY/ES62NWdk1KeSyYvDz7O55C8CexKW1jOF0J9hNE3YPRrOjZd7jvzk23j gQVIofAKSUc+hmr4n04jzJ/TFSqrrHNv8Ys/QtiEbYlYtb9aUpz1MylY5+V8NabJTg 9QaZ/FGbyMuGdiFgoRN0kEXXKtbc5yBQZpLy/4Tg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Lorenz Bauer , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann Subject: [PATCH 5.11 053/210] bpf: link: Refuse non-O_RDWR flags in BPF_OBJ_GET Date: Mon, 12 Apr 2021 10:39:18 +0200 Message-Id: <20210412084017.771117815@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210412084016.009884719@linuxfoundation.org> References: <20210412084016.009884719@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lorenz Bauer commit 25fc94b2f02d832fa8e29419699dcc20b0b05c6a upstream. 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 Signed-off-by: Alexei Starovoitov Acked-by: Andrii Nakryiko Acked-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20210326160501.46234-1-lmb@cloudflare.com Signed-off-by: Greg Kroah-Hartman --- kernel/bpf/inode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/bpf/inode.c +++ b/kernel/bpf/inode.c @@ -546,7 +546,7 @@ int bpf_obj_get_user(const char __user * 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;