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Commit e48d1174 authored by Christian Brauner's avatar Christian Brauner Committed by Greg Kroah-Hartman
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binderfs: add stress test for binderfs binder devices 

This adds a stress test that should hopefully help us catch regressions
for [1], [2], and [3].

[1]: 2669b8b0 ("binder: prevent UAF for binderfs devices")
[2]: f0fe2c0f ("binder: prevent UAF for binderfs devices II")
[3]: 211b64e4 ("binderfs: use refcount for binder control devices too")
Signed-off-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200313152420.138777-3-christian.brauner@ubuntu.comSigned-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent ad29ace2
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Showing with 334 additions and 94 deletions
tools/testing/selftests/filesystems/binderfs/Makefile
View file @ e48d1174
# SPDX-License-Identifier: GPL-2.0
CFLAGS += -I../../../../../usr/include/
CFLAGS += -I../../../../../usr/include/ -pthread
TEST_GEN_PROGS := binderfs_test
binderfs_test: binderfs_test.c ../../kselftest.h ../../kselftest_harness.h
......
tools/testing/selftests/filesystems/binderfs/binderfs_test.c
View file @ e48d1174
......@@ -3,15 +3,20 @@
#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <sched.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/fsuid.h>
#include <sys/ioctl.h>
#include <sys/mount.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/sysinfo.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <linux/android/binder.h>
#include <linux/android/binderfs.h>
......@@ -19,100 +24,26 @@
#include "../../kselftest.h"
#include "../../kselftest_harness.h"
static ssize_t write_nointr(int fd, const void *buf, size_t count)
{
ssize_t ret;
again:
ret = write(fd, buf, count);
if (ret < 0 && errno == EINTR)
goto again;
#define DEFAULT_THREADS 4
return ret;
}
static void write_to_file(const char *filename, const void *buf, size_t count,
int allowed_errno)
{
int fd, saved_errno;
ssize_t ret;
#define PTR_TO_INT(p) ((int)((intptr_t)(p)))
#define INT_TO_PTR(u) ((void *)((intptr_t)(u)))
fd = open(filename, O_WRONLY | O_CLOEXEC);
if (fd < 0)
ksft_exit_fail_msg("%s - Failed to open file %s\n",
strerror(errno), filename);
ret = write_nointr(fd, buf, count);
if (ret < 0) {
if (allowed_errno && (errno == allowed_errno)) {
close(fd);
return;
#define close_prot_errno_disarm(fd) \
if (fd >= 0) { \
int _e_ = errno; \
close(fd); \
errno = _e_; \
fd = -EBADF; \
}
goto on_error;
}
if ((size_t)ret != count)
goto on_error;
close(fd);
return;
on_error:
saved_errno = errno;
close(fd);
errno = saved_errno;
#define log_exit(format, ...) \
({ \
fprintf(stderr, format "\n", ##__VA_ARGS__); \
exit(EXIT_FAILURE); \
})
if (ret < 0)
ksft_exit_fail_msg("%s - Failed to write to file %s\n",
strerror(errno), filename);
ksft_exit_fail_msg("Failed to write to file %s\n", filename);
}
static void change_to_userns(void)
{
int ret;
uid_t uid;
gid_t gid;
/* {g,u}id_map files only allow a max of 4096 bytes written to them */
char idmap[4096];
uid = getuid();
gid = getgid();
ret = unshare(CLONE_NEWUSER);
if (ret < 0)
ksft_exit_fail_msg("%s - Failed to unshare user namespace\n",
strerror(errno));
write_to_file("/proc/self/setgroups", "deny", strlen("deny"), ENOENT);
ret = snprintf(idmap, sizeof(idmap), "0 %d 1", uid);
if (ret < 0 || (size_t)ret >= sizeof(idmap))
ksft_exit_fail_msg("%s - Failed to prepare uid mapping\n",
strerror(errno));
write_to_file("/proc/self/uid_map", idmap, strlen(idmap), 0);
ret = snprintf(idmap, sizeof(idmap), "0 %d 1", gid);
if (ret < 0 || (size_t)ret >= sizeof(idmap))
ksft_exit_fail_msg("%s - Failed to prepare uid mapping\n",
strerror(errno));
write_to_file("/proc/self/gid_map", idmap, strlen(idmap), 0);
ret = setgid(0);
if (ret)
ksft_exit_fail_msg("%s - Failed to setgid(0)\n",
strerror(errno));
ret = setuid(0);
if (ret)
ksft_exit_fail_msg("%s - Failed to setgid(0)\n",
strerror(errno));
}
static void change_to_mountns(void)
static void change_mountns(void)
{
int ret;
......@@ -144,7 +75,7 @@ static int __do_binderfs_test(void)
char binderfs_mntpt[] = P_tmpdir "/binderfs_XXXXXX",
device_path[sizeof(P_tmpdir "/binderfs_XXXXXX/") + BINDERFS_MAX_NAME];
change_to_mountns();
change_mountns();
if (!mkdtemp(binderfs_mntpt))
ksft_exit_fail_msg(
......@@ -253,6 +184,288 @@ static int __do_binderfs_test(void)
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);
}
static int setid_userns_root(void)
{
if (setuid(0))
return -1;
if (setgid(0))
return -1;
setfsuid(0);
setfsgid(0);
return 0;
}
enum idmap_type {
UID_MAP,
GID_MAP,
};
static ssize_t read_nointr(int fd, void *buf, size_t count)
{
ssize_t ret;
again:
ret = read(fd, buf, count);
if (ret < 0 && errno == EINTR)
goto again;
return ret;
}
static ssize_t write_nointr(int fd, const void *buf, size_t count)
{
ssize_t ret;
again:
ret = write(fd, buf, count);
if (ret < 0 && errno == EINTR)
goto again;
return ret;
}
static int write_id_mapping(enum idmap_type type, pid_t pid, const char *buf,
size_t buf_size)
{
int fd;
int ret;
char path[4096];
if (type == GID_MAP) {
int setgroups_fd;
snprintf(path, sizeof(path), "/proc/%d/setgroups", pid);
setgroups_fd = open(path, O_WRONLY | O_CLOEXEC | O_NOFOLLOW);
if (setgroups_fd < 0 && errno != ENOENT)
return -1;
if (setgroups_fd >= 0) {
ret = write_nointr(setgroups_fd, "deny", sizeof("deny") - 1);
close_prot_errno_disarm(setgroups_fd);
if (ret != sizeof("deny") - 1)
return -1;
}
}
switch (type) {
case UID_MAP:
ret = snprintf(path, sizeof(path), "/proc/%d/uid_map", pid);
break;
case GID_MAP:
ret = snprintf(path, sizeof(path), "/proc/%d/gid_map", pid);
break;
default:
return -1;
}
if (ret < 0 || ret >= sizeof(path))
return -E2BIG;
fd = open(path, O_WRONLY | O_CLOEXEC | O_NOFOLLOW);
if (fd < 0)
return -1;
ret = write_nointr(fd, buf, buf_size);
close_prot_errno_disarm(fd);
if (ret != buf_size)
return -1;
return 0;
}
static void change_userns(int syncfds[2])
{
int ret;
char buf;
close_prot_errno_disarm(syncfds[1]);
ret = unshare(CLONE_NEWUSER);
if (ret < 0)
ksft_exit_fail_msg("%s - Failed to unshare user namespace\n",
strerror(errno));
ret = write_nointr(syncfds[0], "1", 1);
if (ret != 1)
ksft_exit_fail_msg("write_nointr() failed\n");
ret = read_nointr(syncfds[0], &buf, 1);
if (ret != 1)
ksft_exit_fail_msg("read_nointr() failed\n");
close_prot_errno_disarm(syncfds[0]);
if (setid_userns_root())
ksft_exit_fail_msg("setid_userns_root() failed");
}
static void change_idmaps(int syncfds[2], pid_t pid)
{
int ret;
char buf;
char id_map[4096];
close_prot_errno_disarm(syncfds[0]);
ret = read_nointr(syncfds[1], &buf, 1);
if (ret != 1)
ksft_exit_fail_msg("read_nointr() failed\n");
snprintf(id_map, sizeof(id_map), "0 %d 1\n", getuid());
ret = write_id_mapping(UID_MAP, pid, id_map, strlen(id_map));
if (ret)
ksft_exit_fail_msg("write_id_mapping(UID_MAP) failed");
snprintf(id_map, sizeof(id_map), "0 %d 1\n", getgid());
ret = write_id_mapping(GID_MAP, pid, id_map, strlen(id_map));
if (ret)
ksft_exit_fail_msg("write_id_mapping(GID_MAP) failed");
ret = write_nointr(syncfds[1], "1", 1);
if (ret != 1)
ksft_exit_fail_msg("write_nointr() failed");
close_prot_errno_disarm(syncfds[1]);
}
static void *binder_version_thread(void *data)
{
int fd = PTR_TO_INT(data);
struct binder_version version = { 0 };
int ret;
ret = ioctl(fd, BINDER_VERSION, &version);
if (ret < 0)
ksft_print_msg("%s - Failed to open perform BINDER_VERSION request\n", strerror(errno));
pthread_exit(data);
}
/*
* Regression test:
* 2669b8b0c798 ("binder: prevent UAF for binderfs devices")
* f0fe2c0f050d ("binder: prevent UAF for binderfs devices II")
* 211b64e4b5b6 ("binderfs: use refcount for binder control devices too")
*/
TEST(binderfs_stress)
{
int fds[1000];
int syncfds[2];
pid_t pid;
int fd, ret;
size_t len;
struct binderfs_device device = { 0 };
char binderfs_mntpt[] = P_tmpdir "/binderfs_XXXXXX",
device_path[sizeof(P_tmpdir "/binderfs_XXXXXX/") + BINDERFS_MAX_NAME];
ret = socketpair(PF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, syncfds);
if (ret < 0)
ksft_exit_fail_msg("%s - Failed to create socket pair", strerror(errno));
pid = fork();
if (pid < 0) {
close_prot_errno_disarm(syncfds[0]);
close_prot_errno_disarm(syncfds[1]);
ksft_exit_fail_msg("%s - Failed to fork", strerror(errno));
}
if (pid == 0) {
int i, j, k, nthreads;
pthread_attr_t attr;
pthread_t threads[DEFAULT_THREADS];
change_userns(syncfds);
change_mountns();
if (!mkdtemp(binderfs_mntpt))
log_exit("%s - Failed to create binderfs mountpoint\n",
strerror(errno));
ret = mount(NULL, binderfs_mntpt, "binder", 0, 0);
if (ret < 0)
log_exit("%s - Failed to mount binderfs\n", strerror(errno));
for (int i = 0; i < ARRAY_SIZE(fds); i++) {
snprintf(device_path, sizeof(device_path),
"%s/binder-control", binderfs_mntpt);
fd = open(device_path, O_RDONLY | O_CLOEXEC);
if (fd < 0)
log_exit("%s - Failed to open binder-control device\n", strerror(errno));
memset(&device, 0, sizeof(device));
snprintf(device.name, sizeof(device.name), "%d", i);
ret = ioctl(fd, BINDER_CTL_ADD, &device);
close_prot_errno_disarm(fd);
if (ret < 0)
log_exit("%s - Failed to allocate new binder device\n", strerror(errno));
snprintf(device_path, sizeof(device_path), "%s/%d",
binderfs_mntpt, i);
fds[i] = open(device_path, O_RDONLY | O_CLOEXEC);
if (fds[i] < 0)
log_exit("%s - Failed to open binder device\n", strerror(errno));
}
ret = umount2(binderfs_mntpt, MNT_DETACH);
rmdir_protect_errno(binderfs_mntpt);
if (ret < 0)
log_exit("%s - Failed to unmount binderfs\n", strerror(errno));
nthreads = get_nprocs_conf();
if (nthreads > DEFAULT_THREADS)
nthreads = DEFAULT_THREADS;
pthread_attr_init(&attr);
for (k = 0; k < ARRAY_SIZE(fds); k++) {
for (i = 0; i < nthreads; i++) {
ret = pthread_create(&threads[i], &attr, binder_version_thread, INT_TO_PTR(fds[k]));
if (ret) {
ksft_print_msg("%s - Failed to create thread %d\n", strerror(errno), i);
break;
}
}
for (j = 0; j < i; j++) {
void *fdptr = NULL;
ret = pthread_join(threads[j], &fdptr);
if (ret)
ksft_print_msg("%s - Failed to join thread %d for fd %d\n", strerror(errno), j, PTR_TO_INT(fdptr));
}
}
pthread_attr_destroy(&attr);
for (k = 0; k < ARRAY_SIZE(fds); k++)
close(fds[k]);
exit(EXIT_SUCCESS);
}
change_idmaps(syncfds, pid);
ret = wait_for_pid(pid);
if (ret)
ksft_exit_fail_msg("wait_for_pid() failed");
}
TEST(binderfs_test_privileged)
{
if (geteuid() != 0)
......@@ -264,10 +477,37 @@ TEST(binderfs_test_privileged)
TEST(binderfs_test_unprivileged)
{
change_to_userns();
int ret;
int syncfds[2];
pid_t pid;
ret = socketpair(PF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, syncfds);
if (ret < 0)
ksft_exit_fail_msg("%s - Failed to create socket pair", strerror(errno));
pid = fork();
if (pid < 0) {
close_prot_errno_disarm(syncfds[0]);
close_prot_errno_disarm(syncfds[1]);
ksft_exit_fail_msg("%s - Failed to fork", strerror(errno));
}
if (pid == 0) {
change_userns(syncfds);
if (__do_binderfs_test() == 1)
exit(2);
exit(EXIT_SUCCESS);
}
change_idmaps(syncfds, pid);
ret = wait_for_pid(pid);
if (ret) {
if (ret == 2)
XFAIL(return, "The Android binderfs filesystem is not available");
else
ksft_exit_fail_msg("wait_for_pid() failed");
}
}
TEST_HARNESS_MAIN
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