From patchwork Mon May 30 08:45:13 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roberto Sassu X-Patchwork-Id: 577398 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 0F478C433EF for ; Mon, 30 May 2022 08:45:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234043AbiE3Ip4 (ORCPT ); Mon, 30 May 2022 04:45:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58226 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230311AbiE3Ipz (ORCPT ); Mon, 30 May 2022 04:45:55 -0400 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AFCA74D601; Mon, 30 May 2022 01:45:54 -0700 (PDT) Received: from fraeml714-chm.china.huawei.com (unknown [172.18.147.200]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4LBTW66dLXz67Y9y; Mon, 30 May 2022 16:45:06 +0800 (CST) Received: from roberto-ThinkStation-P620.huawei.com (10.204.63.22) by fraeml714-chm.china.huawei.com (10.206.15.33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Mon, 30 May 2022 10:45:52 +0200 From: Roberto Sassu To: , , , CC: , , , , Roberto Sassu Subject: [PATCH 1/2] libbpf: Retry map access with read-only permission Date: Mon, 30 May 2022 10:45:13 +0200 Message-ID: <20220530084514.10170-2-roberto.sassu@huawei.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220530084514.10170-1-roberto.sassu@huawei.com> References: <20220530084514.10170-1-roberto.sassu@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.204.63.22] X-ClientProxiedBy: lhreml753-chm.china.huawei.com (10.201.108.203) To fraeml714-chm.china.huawei.com (10.206.15.33) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Retry map access with read-only permission, if access was denied when all permissions were requested (open_flags is set to zero). Write access might have been denied by the bpf_map security hook. Some operations, such as show and dump, don't need write permissions, so there is a good chance of success with retrying. Prefer this solution to extending the API, as otherwise a new mechanism would need to be implemented to determine the right permissions for an operation. Signed-off-by: Roberto Sassu --- tools/lib/bpf/bpf.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c index 240186aac8e6..b4eec39021a4 100644 --- a/tools/lib/bpf/bpf.c +++ b/tools/lib/bpf/bpf.c @@ -1056,6 +1056,11 @@ int bpf_map_get_fd_by_id(__u32 id) attr.map_id = id; fd = sys_bpf_fd(BPF_MAP_GET_FD_BY_ID, &attr, sizeof(attr)); + if (fd < 0) { + attr.open_flags = BPF_F_RDONLY; + fd = sys_bpf_fd(BPF_MAP_GET_FD_BY_ID, &attr, sizeof(attr)); + } + return libbpf_err_errno(fd); } From patchwork Mon May 30 08:45:14 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roberto Sassu X-Patchwork-Id: 577397 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 0A226C4321E for ; Mon, 30 May 2022 08:45:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234056AbiE3Ip5 (ORCPT ); Mon, 30 May 2022 04:45:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58234 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233523AbiE3Ip4 (ORCPT ); Mon, 30 May 2022 04:45:56 -0400 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6C4D052B3A; Mon, 30 May 2022 01:45:55 -0700 (PDT) Received: from fraeml714-chm.china.huawei.com (unknown [172.18.147.206]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4LBTR21D2wz685ZP; Mon, 30 May 2022 16:41:34 +0800 (CST) Received: from roberto-ThinkStation-P620.huawei.com (10.204.63.22) by fraeml714-chm.china.huawei.com (10.206.15.33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Mon, 30 May 2022 10:45:53 +0200 From: Roberto Sassu To: , , , CC: , , , , Roberto Sassu Subject: [PATCH 2/2] selftests/bpf: Add test for retrying access to map with read-only perm Date: Mon, 30 May 2022 10:45:14 +0200 Message-ID: <20220530084514.10170-3-roberto.sassu@huawei.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220530084514.10170-1-roberto.sassu@huawei.com> References: <20220530084514.10170-1-roberto.sassu@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.204.63.22] X-ClientProxiedBy: lhreml753-chm.china.huawei.com (10.201.108.203) To fraeml714-chm.china.huawei.com (10.206.15.33) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Add a test to check the ability of bpf_map_get_fd_by_id() to get a map file descriptor if write permission is denied. Also ensure that a map update operation fails with the obtained read-only file descriptor. Signed-off-by: Roberto Sassu --- .../bpf/prog_tests/test_map_retry_access.c | 54 +++++++++++++++++++ .../selftests/bpf/progs/map_retry_access.c | 36 +++++++++++++ 2 files changed, 90 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/test_map_retry_access.c create mode 100644 tools/testing/selftests/bpf/progs/map_retry_access.c diff --git a/tools/testing/selftests/bpf/prog_tests/test_map_retry_access.c b/tools/testing/selftests/bpf/prog_tests/test_map_retry_access.c new file mode 100644 index 000000000000..beffb2026dcd --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/test_map_retry_access.c @@ -0,0 +1,54 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* + * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH + * + * Author: Roberto Sassu + */ + +#include + +#include "map_retry_access.skel.h" + +void test_test_map_retry_access(void) +{ + struct map_retry_access *skel; + struct bpf_map_info info; + struct bpf_map *map; + __u32 len = sizeof(info); + int ret, zero = 0, fd, duration = 0; + + skel = map_retry_access__open_and_load(); + if (CHECK(!skel, "skel", "open_and_load failed\n")) + goto close_prog; + + ret = map_retry_access__attach(skel); + if (CHECK(ret < 0, "skel", "attach failed\n")) + goto close_prog; + + map = bpf_object__find_map_by_name(skel->obj, "data_input"); + if (CHECK(!map, "bpf_object__find_map_by_name", "not found\n")) + goto close_prog; + + ret = bpf_obj_get_info_by_fd(bpf_map__fd(map), &info, &len); + if (CHECK(ret < 0, "bpf_obj_get_info_by_fd", "error: %d\n", ret)) + goto close_prog; + + fd = bpf_map_get_fd_by_id(info.id); + if (CHECK(fd < 0, "bpf_map_get_fd_by_id", "error: %d\n", fd)) + goto close_prog; + + ret = bpf_map_update_elem(fd, &zero, &len, BPF_ANY); + + close(fd); + + if (CHECK(!ret, "bpf_map_update_elem", + "should fail (read-only permission)\n")) + goto close_prog; + + ret = bpf_map_update_elem(bpf_map__fd(map), &zero, &len, BPF_ANY); + + CHECK(ret < 0, "bpf_map_update_elem", "error: %d\n", ret); +close_prog: + map_retry_access__destroy(skel); +} diff --git a/tools/testing/selftests/bpf/progs/map_retry_access.c b/tools/testing/selftests/bpf/progs/map_retry_access.c new file mode 100644 index 000000000000..1ed7b137a286 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/map_retry_access.c @@ -0,0 +1,36 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* + * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH + * + * Author: Roberto Sassu + */ + +#include "vmlinux.h" +#include +#include +#include + +/* From include/linux/mm.h. */ +#define FMODE_WRITE 0x2 + +struct { + __uint(type, BPF_MAP_TYPE_ARRAY); + __uint(max_entries, 1); + __type(key, __u32); + __type(value, __u32); +} data_input SEC(".maps"); + +char _license[] SEC("license") = "GPL"; + +SEC("lsm/bpf_map") +int BPF_PROG(bpf_map_retry_access, struct bpf_map *map, fmode_t fmode) +{ + if (map != (struct bpf_map *)&data_input) + return 0; + + if (fmode & FMODE_WRITE) + return -EACCES; + + return 0; +}