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Date: Tue, 24 Aug 2021 14:05:23 +0200
From: Christian Brauner <christian.brauner@...ntu.com>
To: Ran Xiaokai <cgel.zte@...il.com>
Cc: dbueso@...e.de, jamorris@...ux.microsoft.com,
keescook@...omium.org, ktkhai@...tuozzo.com, legion@...nel.org,
linux-kernel@...r.kernel.org, ran.xiaokai@....com.cn,
varad.gautam@...e.com
Subject: Re: [PATCH] tests: add mqueue sysctl tests for user namespace
On Sun, Aug 22, 2021 at 08:29:09PM -0700, Ran Xiaokai wrote:
> when a ipc namespace is created in a user namespace, the mqueue sysctl
> files should be writalbe to the owner of the user namespace. Even the
> owner is not a global privileged user.
>
> Signed-off-by: Ran Xiaokai <ran.xiaokai@....com.cn>
> ---
Ran,
Sorry for not replying to your other mail earlier. I read it but I
simply did not have time to respond in any meaningful way to it.
Assuming the test-run works and David is happy with the test too I can
pick it up together with the main patch.
> tools/testing/selftests/Makefile | 1 +
> tools/testing/selftests/mqueue_sysctl/Makefile | 7 +
> tools/testing/selftests/mqueue_sysctl/config | 2 +
> .../selftests/mqueue_sysctl/mq_sysctl_test.c | 172 +++++++++++++++++++++
I think you need to add the binary to .gitignore btw.
> 4 files changed, 182 insertions(+)
> create mode 100644 tools/testing/selftests/mqueue_sysctl/Makefile
> create mode 100644 tools/testing/selftests/mqueue_sysctl/config
> create mode 100644 tools/testing/selftests/mqueue_sysctl/mq_sysctl_test.c
>
> diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
> index bc3299a..2031591 100644
> --- a/tools/testing/selftests/Makefile
> +++ b/tools/testing/selftests/Makefile
> @@ -36,6 +36,7 @@ TARGETS += mincore
> TARGETS += mount
> TARGETS += mount_setattr
> TARGETS += mqueue
> +TARGETS += mqueue_sysctl
> TARGETS += nci
> TARGETS += net
> TARGETS += net/forwarding
> diff --git a/tools/testing/selftests/mqueue_sysctl/Makefile b/tools/testing/selftests/mqueue_sysctl/Makefile
> new file mode 100644
> index 0000000..44b6633
> --- /dev/null
> +++ b/tools/testing/selftests/mqueue_sysctl/Makefile
> @@ -0,0 +1,7 @@
> +# SPDX-License-Identifier: GPL-2.0
> +CFLAGS += -O2
> +LDLIBS = -lrt
> +
> +TEST_GEN_PROGS := mq_sysctl_test
> +
> +include ../lib.mk
> diff --git a/tools/testing/selftests/mqueue_sysctl/config b/tools/testing/selftests/mqueue_sysctl/config
> new file mode 100644
> index 0000000..68b2794
> --- /dev/null
> +++ b/tools/testing/selftests/mqueue_sysctl/config
> @@ -0,0 +1,2 @@
> +CONFIG_USER_NS=y
> +CONFIG_POSIX_MQUEUE_SYSCTL=y
> \ No newline at end of file
> diff --git a/tools/testing/selftests/mqueue_sysctl/mq_sysctl_test.c b/tools/testing/selftests/mqueue_sysctl/mq_sysctl_test.c
> new file mode 100644
> index 0000000..48023d5
> --- /dev/null
> +++ b/tools/testing/selftests/mqueue_sysctl/mq_sysctl_test.c
> @@ -0,0 +1,172 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#define _GNU_SOURCE
> +#include <stdio.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <fcntl.h>
> +#include <unistd.h>
> +#include <errno.h>
> +#include <sched.h>
> +#include <sys/mount.h>
> +#include <mqueue.h>
> +#include <sys/wait.h>
> +#include <string.h>
> +
> +#include "../kselftest_harness.h"
> +
> +static ssize_t write_nointr(int fd, const void *buf, size_t count)
> +{
> + ssize_t ret;
> +
> + do {
> + ret = write(fd, buf, count);
> + } while (ret < 0 && errno == EINTR);
> +
> + return ret;
> +}
> +
> +static int write_file(const char *path, const void *buf, size_t count)
> +{
> + int fd;
> + ssize_t ret;
> +
> + fd = open(path, O_WRONLY | O_CLOEXEC | O_NOCTTY | O_NOFOLLOW);
> + if (fd < 0)
> + return -1;
> +
> + ret = write_nointr(fd, buf, count);
> + close(fd);
> + if (ret < 0 || (size_t)ret != count)
> + return -1;
> +
> + return 0;
> +}
> +
> +static int create_and_enter_userns(void)
> +{
> + uid_t uid;
> + gid_t gid;
> + char map[100];
> +
> + uid = getuid();
> + gid = getgid();
> +
> + if (unshare(CLONE_NEWUSER))
> + return -1;
> +
> + if (write_file("/proc/self/setgroups", "deny", sizeof("deny") - 1) &&
> + errno != ENOENT)
> + return -1;
> +
> + snprintf(map, sizeof(map), "0 %d 1", uid);
> + if (write_file("/proc/self/uid_map", map, strlen(map)))
> + return -1;
> +
> + snprintf(map, sizeof(map), "0 %d 1", gid);
> + if (write_file("/proc/self/gid_map", map, strlen(map)))
> + return -1;
> +
> + if (setgid(0))
> + return -1;
> +
> + if (setuid(0))
> + return -1;
> +
> + return 0;
> +}
> +
> +static int prepare_unpriv_mountns(void)
> +{
> + if (create_and_enter_userns())
> + return -1;
> +
> + if (unshare(CLONE_NEWNS))
> + return -1;
> +
> + if (mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, 0))
> + return -1;
> +
> + if (unshare(CLONE_NEWIPC))
> + return -1;
> +
> + return 0;
> +}
> +
> +static int wait_for_pid(pid_t pid)
> +{
> + int status, ret;
> +
> +again:
> + ret = waitpid(pid, &status, 0);
> + if (ret == -1) {
> + if (errno == EINTR)
> + goto again;
> +
> + return -1;
> + }
> +
> + if (!WIFEXITED(status))
> + return -1;
> +
> + return WEXITSTATUS(status);
> +}
> +
> +int get_mq_queues_max(void)
can be made static
> +{
> + int fd;
> + char buf[16];
> + int val = -1;
> +
> + fd = open("/proc/sys/fs/mqueue/queues_max", O_RDONLY);
> + if (fd >= 0) {
> + if (read(fd, buf, sizeof(buf)) > 0)
> + val = atoi(buf);
> +
> + close(fd);
> + return val;
> + }
> + return val;
> +}
> +
> +TEST(mqueue_sysctl)
> +{
> + pid_t pid;
> + int qmax1, qmax2;
> +
> + chdir(getenv("HOME"));
Hm, don't do that. I would suggest using a temporary directory. Sm like:
char template[] = P_tmpdir "/mqueue_sysctl_XXXXXX";
if (!mkdtemp(template))
// handle error
int fd = openat(-1, template, O_CLOEXEC | O_DIRECTORY);
mkdirat(fd, "mqueue", ...);
and then at exit:
unlinkat(fd, "mqueue", AT_REMOVEDIR);
remove(template);
etc.
Christian
> + /* read and stash the original sysctl value */
> + qmax1 = get_mq_queues_max();
> + ASSERT_GE(qmax1, 0);
> +
> + pid = fork();
> + ASSERT_GE(pid, 0);
> +
> + if (pid == 0) {
> + ASSERT_EQ(prepare_unpriv_mountns(), 0);
> +
> + if (mkdir("./mqueue", 755) && errno != EEXIST)
> + SKIP(return, "mkdir /dev/mqueue failed");
> +
> + ASSERT_EQ(mount("none", "./mqueue", "mqueue", MS_NOATIME, NULL), 0);
> +
> + /* modify the sysctl value in new ipc namesapce */
> + ASSERT_EQ(write_file("/proc/sys/fs/mqueue/queues_max", "1", 1), 0);
> +
> + ASSERT_GE(mq_open("/new_ns1", O_RDWR | O_CREAT, 0644, NULL), 0);
> +
> + /* mq_open() should fail as exceeding of queues_max */
> + ASSERT_EQ(mq_open("/new_ns2", O_RDWR | O_CREAT, 0644, NULL), -1);
> +
> + ASSERT_EQ(mq_unlink("/new_ns1"), 0);
> + ASSERT_EQ(umount("./mqueue"), 0);
> +
> + exit(0);
> + }
> +
> + ASSERT_EQ(wait_for_pid(pid), 0);
> +
> + qmax2 = get_mq_queues_max();
> + ASSERT_EQ(qmax1, qmax2);
> +}
> +
> +TEST_HARNESS_MAIN
> --
> 2.15.2
>
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