From patchwork Thu Aug 27 17:09:47 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ross Zwisler X-Patchwork-Id: 11741123 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D698813B1 for ; Thu, 27 Aug 2020 17:10:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B2FEB22B4D for ; Thu, 27 Aug 2020 17:10:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="YKb3uzdI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726009AbgH0RKE (ORCPT ); Thu, 27 Aug 2020 13:10:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55102 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726217AbgH0RKB (ORCPT ); Thu, 27 Aug 2020 13:10:01 -0400 Received: from mail-io1-xd44.google.com (mail-io1-xd44.google.com [IPv6:2607:f8b0:4864:20::d44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4E2F4C061233 for ; Thu, 27 Aug 2020 10:10:00 -0700 (PDT) Received: by mail-io1-xd44.google.com with SMTP id s2so6624266ioo.2 for ; Thu, 27 Aug 2020 10:10:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=JueOAVgNYgqbWYVYqLooj1vIHH/WeKWbvTedzr6nkHI=; b=YKb3uzdI72no6P2AMeLmB/dQ7L5o4c89fhaInwgUEQzNIl3gqfWzfygxqN9yuB7NnO 1La7m8T0c4shQtFDVoltp4emyuNj4ozrOcdlPivRM6j9BEx3d172BPAHSzCd0xYfM7Fg fXn/li9z6G+ll/lP1jZPEcJS01PYlySWTPpkw= 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:in-reply-to :references:mime-version:content-transfer-encoding; bh=JueOAVgNYgqbWYVYqLooj1vIHH/WeKWbvTedzr6nkHI=; b=Agt9HI2RDgQq/PR67/WWTUBa7qXBhWS/GOA0wGcv4KOg8f/2vo1O1+4BMkGAHPsgo6 HH1PYoANzYxmL7P9kvCgSMffi34wIBStqHhhlPZoJMl/02ZubGGVBtFP37RgAWw4qzxT OWVwEjhwmD6JDl/3ikV7CXc8DWOU0qtMDlXOSO5CpBBGJ1ysMW92lPVadYv39BFDAxvU kZmzk7+6KUZsyNK9DMOa+NMR0SQPSaaWzW/3r6sdB60GYo0acMf/OZqE7hl5OmM+QAEw qxd4g8u9nE7YLZHqyl1lbRsfXixX9EuUuG/Dqecyof6KlUBQZ4mlkjbtPZPIvoSCx+kd gITg== X-Gm-Message-State: AOAM530cStUk4bD/0kuKdcU2TD0JMw/9/Y51ayQeBiKf6dRotR+lOIQx 9Ddj1dSklR1pCMfcQYN8pgb16Q== X-Google-Smtp-Source: ABdhPJwgdpRQdR/omvo7NV4K3vZad1KgZMYV8A3SZEKwH4TFMRbIRvi58Y6c3e2vKc0zdS3D1L7yBg== X-Received: by 2002:a6b:681a:: with SMTP id d26mr17763852ioc.70.1598548199537; Thu, 27 Aug 2020 10:09:59 -0700 (PDT) Received: from ravnica.hsd1.co.comcast.net ([2601:285:8380:9270::f2a2]) by smtp.gmail.com with ESMTPSA id 137sm1501157ioc.20.2020.08.27.10.09.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Aug 2020 10:09:58 -0700 (PDT) From: Ross Zwisler X-Google-Original-From: Ross Zwisler To: Alexander Viro , linux-kernel@vger.kernel.org Cc: Ross Zwisler , Mattias Nissler , Aleksa Sarai , Andrew Morton , Benjamin Gordon , David Howells , Dmitry Torokhov , Jesse Barnes , linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org, Matthew Wilcox , Micah Morton , Raul Rangel , Shuah Khan Subject: [PATCH v9 2/2] selftests: mount: add nosymfollow tests Date: Thu, 27 Aug 2020 11:09:47 -0600 Message-Id: <20200827170947.429611-2-zwisler@google.com> X-Mailer: git-send-email 2.28.0.297.g1956fa8f8d-goog In-Reply-To: <20200827170947.429611-1-zwisler@google.com> References: <20200827170947.429611-1-zwisler@google.com> MIME-Version: 1.0 Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Add tests for the new 'nosymfollow' mount option. We test to make sure that symlink traversal fails with ELOOP when 'nosymfollow' is set, but that readlink(2) and realpath(3) still work as expected. We also verify that statfs(2) correctly returns ST_NOSYMFOLLOW when we are mounted with the 'nosymfollow' option. Signed-off-by: Ross Zwisler --- tools/testing/selftests/mount/.gitignore | 1 + tools/testing/selftests/mount/Makefile | 4 +- .../selftests/mount/nosymfollow-test.c | 218 ++++++++++++++++++ .../selftests/mount/run_nosymfollow.sh | 4 + ...n_tests.sh => run_unprivileged_remount.sh} | 0 5 files changed, 225 insertions(+), 2 deletions(-) create mode 100644 tools/testing/selftests/mount/nosymfollow-test.c create mode 100755 tools/testing/selftests/mount/run_nosymfollow.sh rename tools/testing/selftests/mount/{run_tests.sh => run_unprivileged_remount.sh} (100%) diff --git a/tools/testing/selftests/mount/.gitignore b/tools/testing/selftests/mount/.gitignore index 0bc64a6d4c181..17f2d84151622 100644 --- a/tools/testing/selftests/mount/.gitignore +++ b/tools/testing/selftests/mount/.gitignore @@ -1,2 +1,3 @@ # SPDX-License-Identifier: GPL-2.0-only unprivileged-remount-test +nosymfollow-test diff --git a/tools/testing/selftests/mount/Makefile b/tools/testing/selftests/mount/Makefile index 026890744215b..2d9454841644a 100644 --- a/tools/testing/selftests/mount/Makefile +++ b/tools/testing/selftests/mount/Makefile @@ -3,7 +3,7 @@ CFLAGS = -Wall \ -O2 -TEST_PROGS := run_tests.sh -TEST_GEN_FILES := unprivileged-remount-test +TEST_PROGS := run_unprivileged_remount.sh run_nosymfollow.sh +TEST_GEN_FILES := unprivileged-remount-test nosymfollow-test include ../lib.mk diff --git a/tools/testing/selftests/mount/nosymfollow-test.c b/tools/testing/selftests/mount/nosymfollow-test.c new file mode 100644 index 0000000000000..650d6d80a1d27 --- /dev/null +++ b/tools/testing/selftests/mount/nosymfollow-test.c @@ -0,0 +1,218 @@ +// SPDX-License-Identifier: GPL-2.0 +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#ifndef MS_NOSYMFOLLOW +# define MS_NOSYMFOLLOW 256 /* Do not follow symlinks */ +#endif + +#ifndef ST_NOSYMFOLLOW +# define ST_NOSYMFOLLOW 0x2000 /* Do not follow symlinks */ +#endif + +#define DATA "/tmp/data" +#define LINK "/tmp/symlink" +#define TMP "/tmp" + +static void die(char *fmt, ...) +{ + va_list ap; + + va_start(ap, fmt); + vfprintf(stderr, fmt, ap); + va_end(ap); + exit(EXIT_FAILURE); +} + +static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, + va_list ap) +{ + ssize_t written; + char buf[4096]; + int buf_len; + int fd; + + buf_len = vsnprintf(buf, sizeof(buf), fmt, ap); + if (buf_len < 0) + die("vsnprintf failed: %s\n", strerror(errno)); + + if (buf_len >= sizeof(buf)) + die("vsnprintf output truncated\n"); + + fd = open(filename, O_WRONLY); + if (fd < 0) { + if ((errno == ENOENT) && enoent_ok) + return; + die("open of %s failed: %s\n", filename, strerror(errno)); + } + + written = write(fd, buf, buf_len); + if (written != buf_len) { + if (written >= 0) { + die("short write to %s\n", filename); + } else { + die("write to %s failed: %s\n", + filename, strerror(errno)); + } + } + + if (close(fd) != 0) + die("close of %s failed: %s\n", filename, strerror(errno)); +} + +static void maybe_write_file(char *filename, char *fmt, ...) +{ + va_list ap; + + va_start(ap, fmt); + vmaybe_write_file(true, filename, fmt, ap); + va_end(ap); +} + +static void write_file(char *filename, char *fmt, ...) +{ + va_list ap; + + va_start(ap, fmt); + vmaybe_write_file(false, filename, fmt, ap); + va_end(ap); +} + +static void create_and_enter_ns(void) +{ + uid_t uid = getuid(); + gid_t gid = getgid(); + + if (unshare(CLONE_NEWUSER) != 0) + die("unshare(CLONE_NEWUSER) failed: %s\n", strerror(errno)); + + maybe_write_file("/proc/self/setgroups", "deny"); + write_file("/proc/self/uid_map", "0 %d 1", uid); + write_file("/proc/self/gid_map", "0 %d 1", gid); + + if (setgid(0) != 0) + die("setgid(0) failed %s\n", strerror(errno)); + if (setuid(0) != 0) + die("setuid(0) failed %s\n", strerror(errno)); + + if (unshare(CLONE_NEWNS) != 0) + die("unshare(CLONE_NEWNS) failed: %s\n", strerror(errno)); +} + +static void setup_symlink(void) +{ + int data, err; + + data = creat(DATA, O_RDWR); + if (data < 0) + die("creat failed: %s\n", strerror(errno)); + + err = symlink(DATA, LINK); + if (err < 0) + die("symlink failed: %s\n", strerror(errno)); + + if (close(data) != 0) + die("close of %s failed: %s\n", DATA, strerror(errno)); +} + +static void test_link_traversal(bool nosymfollow) +{ + int link; + + link = open(LINK, 0, O_RDWR); + if (nosymfollow) { + if ((link != -1 || errno != ELOOP)) { + die("link traversal unexpected result: %d, %s\n", + link, strerror(errno)); + } + } else { + if (link < 0) + die("link traversal failed: %s\n", strerror(errno)); + + if (close(link) != 0) + die("close of link failed: %s\n", strerror(errno)); + } +} + +static void test_readlink(void) +{ + char buf[4096]; + ssize_t ret; + + bzero(buf, sizeof(buf)); + + ret = readlink(LINK, buf, sizeof(buf)); + if (ret < 0) + die("readlink failed: %s\n", strerror(errno)); + if (strcmp(buf, DATA) != 0) + die("readlink strcmp failed: '%s' '%s'\n", buf, DATA); +} + +static void test_realpath(void) +{ + char *path = realpath(LINK, NULL); + + if (!path) + die("realpath failed: %s\n", strerror(errno)); + if (strcmp(path, DATA) != 0) + die("realpath strcmp failed\n"); + + free(path); +} + +static void test_statfs(bool nosymfollow) +{ + struct statfs buf; + int ret; + + ret = statfs(TMP, &buf); + if (ret) + die("statfs failed: %s\n", strerror(errno)); + + if (nosymfollow) { + if ((buf.f_flags & ST_NOSYMFOLLOW) == 0) + die("ST_NOSYMFOLLOW not set on %s\n", TMP); + } else { + if ((buf.f_flags & ST_NOSYMFOLLOW) != 0) + die("ST_NOSYMFOLLOW set on %s\n", TMP); + } +} + +static void run_tests(bool nosymfollow) +{ + test_link_traversal(nosymfollow); + test_readlink(); + test_realpath(); + test_statfs(nosymfollow); +} + +int main(int argc, char **argv) +{ + create_and_enter_ns(); + + if (mount("testing", TMP, "ramfs", 0, NULL) != 0) + die("mount failed: %s\n", strerror(errno)); + + setup_symlink(); + run_tests(false); + + if (mount("testing", TMP, "ramfs", MS_REMOUNT|MS_NOSYMFOLLOW, NULL) != 0) + die("remount failed: %s\n", strerror(errno)); + + run_tests(true); + + return EXIT_SUCCESS; +} diff --git a/tools/testing/selftests/mount/run_nosymfollow.sh b/tools/testing/selftests/mount/run_nosymfollow.sh new file mode 100755 index 0000000000000..5fbbf03043a2e --- /dev/null +++ b/tools/testing/selftests/mount/run_nosymfollow.sh @@ -0,0 +1,4 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 + +./nosymfollow-test diff --git a/tools/testing/selftests/mount/run_tests.sh b/tools/testing/selftests/mount/run_unprivileged_remount.sh similarity index 100% rename from tools/testing/selftests/mount/run_tests.sh rename to tools/testing/selftests/mount/run_unprivileged_remount.sh