Check that a uid_map or gid_map line with a value that does not fit in u32 is rejected with EINVAL and installs nothing, for each of the three fields, and that an in-range line is still accepted and reads back unchanged.
Signed-off-by: Natasha Klaus <[email protected]> Assisted-by: LLM --- tools/testing/selftests/namespaces/.gitignore | 1 + tools/testing/selftests/namespaces/Makefile | 3 +- .../selftests/namespaces/uid_map_range_test.c | 155 ++++++++++++++++++ 3 files changed, 158 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/namespaces/uid_map_range_test.c diff --git a/tools/testing/selftests/namespaces/.gitignore b/tools/testing/selftests/namespaces/.gitignore index 0989e80da457..995b082357fa 100644 --- a/tools/testing/selftests/namespaces/.gitignore +++ b/tools/testing/selftests/namespaces/.gitignore @@ -10,3 +10,4 @@ cred_change_test stress_test listns_pagination_bug regression_pidfd_setns_test +uid_map_range_test diff --git a/tools/testing/selftests/namespaces/Makefile b/tools/testing/selftests/namespaces/Makefile index fbb821652c17..9b22d12708e1 100644 --- a/tools/testing/selftests/namespaces/Makefile +++ b/tools/testing/selftests/namespaces/Makefile @@ -13,7 +13,8 @@ TEST_GEN_PROGS := nsid_test \ cred_change_test \ stress_test \ listns_pagination_bug \ - regression_pidfd_setns_test + regression_pidfd_setns_test \ + uid_map_range_test include ../lib.mk diff --git a/tools/testing/selftests/namespaces/uid_map_range_test.c b/tools/testing/selftests/namespaces/uid_map_range_test.c new file mode 100644 index 000000000000..9da02005a09c --- /dev/null +++ b/tools/testing/selftests/namespaces/uid_map_range_test.c @@ -0,0 +1,155 @@ +// SPDX-License-Identifier: GPL-2.0 +#define _GNU_SOURCE +#include <errno.h> +#include <fcntl.h> +#include <sched.h> +#include <stdio.h> +#include <string.h> +#include <unistd.h> +#include "../kselftest_harness.h" + +/* + * The fields of a uid_map/gid_map line are stored in u32. Values that + * do not fit must be rejected with EINVAL instead of being silently + * truncated modulo 2^32, and in-range values must still be accepted. + */ + +static int write_file(const char *path, const char *buf) +{ + ssize_t len = strlen(buf); + ssize_t ret; + int fd; + + fd = open(path, O_WRONLY | O_CLOEXEC); + if (fd < 0) + return -errno; + ret = write(fd, buf, len); + if (ret < 0) + ret = -errno; + close(fd); + if (ret < 0) + return ret; + return ret == len ? 0 : -EIO; +} + +static ssize_t read_file(const char *path, char *buf, size_t size) +{ + ssize_t ret; + int fd; + + fd = open(path, O_RDONLY | O_CLOEXEC); + if (fd < 0) + return -errno; + ret = read(fd, buf, size - 1); + if (ret < 0) + ret = -errno; + else + buf[ret] = '\0'; + close(fd); + return ret; +} + +/* Enter a fresh user namespace, remembering the outer ids. */ +static int enter_userns(uid_t *uid, gid_t *gid) +{ + *uid = geteuid(); + *gid = getegid(); + if (unshare(CLONE_NEWUSER) < 0) + return -errno; + /* Required before an unprivileged gid_map write. */ + return write_file("/proc/self/setgroups", "deny"); +} + +static void expect_rejected(struct __test_metadata *_metadata, + const char *path, const char *line) +{ + char buf[256]; + + TH_LOG("writing \"%s\" to %s", line, path); + EXPECT_EQ(write_file(path, line), -EINVAL); + /* Nothing may have been installed. */ + EXPECT_EQ(read_file(path, buf, sizeof(buf)), 0) { + TH_LOG("installed: %s", buf); + } +} + +TEST(uid_map_first_above_u32) +{ + char line[64]; + uid_t uid; + gid_t gid; + int ret; + + ret = enter_userns(&uid, &gid); + if (ret) + SKIP(return, "cannot set up user namespace: %s", strerror(-ret)); + snprintf(line, sizeof(line), "4294967301 %u 1", uid); + expect_rejected(_metadata, "/proc/self/uid_map", line); +} + +TEST(uid_map_lower_first_above_u32) +{ + char line[64]; + uid_t uid; + gid_t gid; + int ret; + + ret = enter_userns(&uid, &gid); + if (ret) + SKIP(return, "cannot set up user namespace: %s", strerror(-ret)); + snprintf(line, sizeof(line), "0 %llu 1", (1ULL << 32) + uid); + expect_rejected(_metadata, "/proc/self/uid_map", line); +} + +TEST(uid_map_count_above_u32) +{ + char line[64]; + uid_t uid; + gid_t gid; + int ret; + + ret = enter_userns(&uid, &gid); + if (ret) + SKIP(return, "cannot set up user namespace: %s", strerror(-ret)); + snprintf(line, sizeof(line), "0 %u 4294967297", uid); + expect_rejected(_metadata, "/proc/self/uid_map", line); +} + +TEST(gid_map_first_above_u32) +{ + char line[64]; + uid_t uid; + gid_t gid; + int ret; + + ret = enter_userns(&uid, &gid); + if (ret) + SKIP(return, "cannot set up user namespace: %s", strerror(-ret)); + snprintf(line, sizeof(line), "4294967301 %u 1", gid); + expect_rejected(_metadata, "/proc/self/gid_map", line); +} + +TEST(uid_map_in_range) +{ + unsigned int first, lower_first, count; + char line[64], buf[256]; + uid_t uid; + gid_t gid; + int ret; + + ret = enter_userns(&uid, &gid); + if (ret) + SKIP(return, "cannot set up user namespace: %s", strerror(-ret)); + snprintf(line, sizeof(line), "5 %u 1", uid); + ASSERT_EQ(write_file("/proc/self/uid_map", line), 0); + + ASSERT_GT(read_file("/proc/self/uid_map", buf, sizeof(buf)), 0); + ASSERT_EQ(sscanf(buf, "%u %u %u", &first, &lower_first, &count), 3); + EXPECT_EQ(first, 5U); + EXPECT_EQ(lower_first, uid); + EXPECT_EQ(count, 1U); + /* Exactly one extent. */ + EXPECT_EQ(strchr(buf, '\n'), buf + strlen(buf) - 1); +} + +TEST_HARNESS_MAIN -- 2.34.1
