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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 5D6D8C433E1 for ; Fri, 3 Jul 2020 18:12:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 495A02084C for ; Fri, 3 Jul 2020 18:12:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726148AbgGCSML (ORCPT ); Fri, 3 Jul 2020 14:12:11 -0400 Received: from mail.hallyn.com ([178.63.66.53]:45006 "EHLO mail.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726147AbgGCSML (ORCPT ); Fri, 3 Jul 2020 14:12:11 -0400 Received: by mail.hallyn.com (Postfix, from userid 1001) id 0C5296FC; Fri, 3 Jul 2020 13:12:09 -0500 (CDT) Date: Fri, 3 Jul 2020 13:12:09 -0500 From: "Serge E. Hallyn" To: Adrian Reber Cc: "Serge E. Hallyn" , Christian Brauner , Eric Biederman , Pavel Emelyanov , Oleg Nesterov , Dmitry Safonov <0x7f454c46@gmail.com>, Andrei Vagin , Nicolas Viennot , =?utf-8?B?TWljaGHFgiBDxYJhcGnFhHNraQ==?= , Kamil Yurtsever , Dirk Petersen , Christine Flood , Casey Schaufler , Mike Rapoport , Radostin Stoyanov , Cyrill Gorcunov , Stephen Smalley , Sargun Dhillon , Arnd Bergmann , linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, selinux@vger.kernel.org, Eric Paris , Jann Horn , linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v4 2/3] selftests: add clone3() CAP_CHECKPOINT_RESTORE test Message-ID: <20200703181208.GA16241@mail.hallyn.com> References: <20200701064906.323185-1-areber@redhat.com> <20200701064906.323185-3-areber@redhat.com> <20200702205305.GA3283@mail.hallyn.com> <20200703111807.GC243637@dcbz.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200703111807.GC243637@dcbz.redhat.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Fri, Jul 03, 2020 at 01:18:07PM +0200, Adrian Reber wrote: > On Thu, Jul 02, 2020 at 03:53:05PM -0500, Serge E. Hallyn wrote: > > On Wed, Jul 01, 2020 at 08:49:05AM +0200, Adrian Reber wrote: > > > This adds a test that changes its UID, uses capabilities to > > > get CAP_CHECKPOINT_RESTORE and uses clone3() with set_tid to > > > create a process with a given PID as non-root. > > > > Seems worth also verifying that it fails if you have no capabilities. > > I don't see that in the existing clone3/ test dir. > > Bit confused about what you mean. This test does: > > * switch UID to 1000 > * run clone3() with set_tid set and expect EPERM > * set CAP_CHECKPOINT_RESTORE capability > * run clone3() with set_tid set and expect success > > So it already does what I think you are asking for. Did I misunderstand > your comment? Ah, no, I missed that line doing the call with -EPERM. Thanks! Acked-by: Serge Hallyn > Adrian > > > > Signed-off-by: Adrian Reber > > > --- > > > tools/testing/selftests/clone3/Makefile | 4 +- > > > .../clone3/clone3_cap_checkpoint_restore.c | 203 ++++++++++++++++++ > > > 2 files changed, 206 insertions(+), 1 deletion(-) > > > create mode 100644 tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c > > > > > > diff --git a/tools/testing/selftests/clone3/Makefile b/tools/testing/selftests/clone3/Makefile > > > index cf976c732906..ef7564cb7abe 100644 > > > --- a/tools/testing/selftests/clone3/Makefile > > > +++ b/tools/testing/selftests/clone3/Makefile > > > @@ -1,6 +1,8 @@ > > > # SPDX-License-Identifier: GPL-2.0 > > > CFLAGS += -g -I../../../../usr/include/ > > > +LDLIBS += -lcap > > > > > > -TEST_GEN_PROGS := clone3 clone3_clear_sighand clone3_set_tid > > > +TEST_GEN_PROGS := clone3 clone3_clear_sighand clone3_set_tid \ > > > + clone3_cap_checkpoint_restore > > > > > > include ../lib.mk > > > diff --git a/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c b/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c > > > new file mode 100644 > > > index 000000000000..2cc3d57b91f2 > > > --- /dev/null > > > +++ b/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c > > > @@ -0,0 +1,203 @@ > > > +// SPDX-License-Identifier: GPL-2.0 > > > + > > > +/* > > > + * Based on Christian Brauner's clone3() example. > > > + * These tests are assuming to be running in the host's > > > + * PID namespace. > > > + */ > > > + > > > +/* capabilities related code based on selftests/bpf/test_verifier.c */ > > > + > > > +#define _GNU_SOURCE > > > +#include > > > +#include > > > +#include > > > +#include > > > +#include > > > +#include > > > +#include > > > +#include > > > +#include > > > +#include > > > +#include > > > +#include > > > +#include > > > +#include > > > + > > > +#include "../kselftest.h" > > > +#include "clone3_selftests.h" > > > + > > > +#ifndef MAX_PID_NS_LEVEL > > > +#define MAX_PID_NS_LEVEL 32 > > > +#endif > > > + > > > +static void child_exit(int ret) > > > +{ > > > + fflush(stdout); > > > + fflush(stderr); > > > + _exit(ret); > > > +} > > > + > > > +static int call_clone3_set_tid(pid_t * set_tid, size_t set_tid_size) > > > +{ > > > + int status; > > > + pid_t pid = -1; > > > + > > > + struct clone_args args = { > > > + .exit_signal = SIGCHLD, > > > + .set_tid = ptr_to_u64(set_tid), > > > + .set_tid_size = set_tid_size, > > > + }; > > > + > > > + pid = sys_clone3(&args, sizeof(struct clone_args)); > > > + if (pid < 0) { > > > + ksft_print_msg("%s - Failed to create new process\n", > > > + strerror(errno)); > > > + return -errno; > > > + } > > > + > > > + if (pid == 0) { > > > + int ret; > > > + char tmp = 0; > > > + > > > + ksft_print_msg > > > + ("I am the child, my PID is %d (expected %d)\n", > > > + getpid(), set_tid[0]); > > > + > > > + if (set_tid[0] != getpid()) > > > + child_exit(EXIT_FAILURE); > > > + child_exit(EXIT_SUCCESS); > > > + } > > > + > > > + ksft_print_msg("I am the parent (%d). My child's pid is %d\n", > > > + getpid(), pid); > > > + > > > + if (waitpid(pid, &status, 0) < 0) { > > > + ksft_print_msg("Child returned %s\n", strerror(errno)); > > > + return -errno; > > > + } > > > + > > > + if (!WIFEXITED(status)) > > > + return -1; > > > + > > > + return WEXITSTATUS(status); > > > +} > > > + > > > +static int test_clone3_set_tid(pid_t * set_tid, > > > + size_t set_tid_size, int expected) > > > +{ > > > + int ret; > > > + > > > + ksft_print_msg("[%d] Trying clone3() with CLONE_SET_TID to %d\n", > > > + getpid(), set_tid[0]); > > > + ret = call_clone3_set_tid(set_tid, set_tid_size); > > > + > > > + ksft_print_msg > > > + ("[%d] clone3() with CLONE_SET_TID %d says :%d - expected %d\n", > > > + getpid(), set_tid[0], ret, expected); > > > + if (ret != expected) { > > > + ksft_test_result_fail > > > + ("[%d] Result (%d) is different than expected (%d)\n", > > > + getpid(), ret, expected); > > > + return -1; > > > + } > > > + ksft_test_result_pass > > > + ("[%d] Result (%d) matches expectation (%d)\n", getpid(), ret, > > > + expected); > > > + > > > + return 0; > > > +} > > > + > > > +struct libcap { > > > + struct __user_cap_header_struct hdr; > > > + struct __user_cap_data_struct data[2]; > > > +}; > > > + > > > +static int set_capability() > > > +{ > > > + cap_value_t cap_values[] = { CAP_SETUID, CAP_SETGID }; > > > + struct libcap *cap; > > > + int ret = -1; > > > + cap_t caps; > > > + > > > + caps = cap_get_proc(); > > > + if (!caps) { > > > + perror("cap_get_proc"); > > > + return -1; > > > + } > > > + > > > + /* Drop all capabilities */ > > > + if (cap_clear(caps)) { > > > + perror("cap_clear"); > > > + goto out; > > > + } > > > + > > > + cap_set_flag(caps, CAP_EFFECTIVE, 2, cap_values, CAP_SET); > > > + cap_set_flag(caps, CAP_PERMITTED, 2, cap_values, CAP_SET); > > > + > > > + cap = (struct libcap *) caps; > > > + > > > + /* 40 -> CAP_CHECKPOINT_RESTORE */ > > > + cap->data[1].effective |= 1 << (40 - 32); > > > + cap->data[1].permitted |= 1 << (40 - 32); > > > + > > > + if (cap_set_proc(caps)) { > > > + perror("cap_set_proc"); > > > + goto out; > > > + } > > > + ret = 0; > > > +out: > > > + if (cap_free(caps)) > > > + perror("cap_free"); > > > + return ret; > > > +} > > > + > > > +int main(int argc, char *argv[]) > > > +{ > > > + pid_t pid; > > > + int status; > > > + int ret = 0; > > > + pid_t set_tid[1]; > > > + uid_t uid = getuid(); > > > + > > > + ksft_print_header(); > > > + test_clone3_supported(); > > > + ksft_set_plan(2); > > > + > > > + if (uid != 0) { > > > + ksft_cnt.ksft_xskip = ksft_plan; > > > + ksft_print_msg("Skipping all tests as non-root\n"); > > > + return ksft_exit_pass(); > > > + } > > > + > > > + memset(&set_tid, 0, sizeof(set_tid)); > > > + > > > + /* Find the current active PID */ > > > + pid = fork(); > > > + if (pid == 0) { > > > + ksft_print_msg("Child has PID %d\n", getpid()); > > > + child_exit(EXIT_SUCCESS); > > > + } > > > + if (waitpid(pid, &status, 0) < 0) > > > + ksft_exit_fail_msg("Waiting for child %d failed", pid); > > > + > > > + /* After the child has finished, its PID should be free. */ > > > + set_tid[0] = pid; > > > + > > > + if (set_capability()) > > > + ksft_test_result_fail > > > + ("Could not set CAP_CHECKPOINT_RESTORE\n"); > > > + prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0); > > > + /* This would fail without CAP_CHECKPOINT_RESTORE */ > > > + setgid(1000); > > > + setuid(1000); > > > + set_tid[0] = pid; > > > + ret |= test_clone3_set_tid(set_tid, 1, -EPERM); > > > + if (set_capability()) > > > + ksft_test_result_fail > > > + ("Could not set CAP_CHECKPOINT_RESTORE\n"); > > > + /* This should work as we have CAP_CHECKPOINT_RESTORE as non-root */ > > > + ret |= test_clone3_set_tid(set_tid, 1, 0); > > > + > > > + return !ret ? ksft_exit_pass() : ksft_exit_fail(); > > > +} > > > -- > > > 2.26.2 > >