| Message ID | 20200312131531.3615556-2-christian.brauner@ubuntu.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [1/3] binderfs: port tests to test harness infrastructure | expand |
On Thu, Mar 12, 2020 at 02:15:30PM +0100, Christian Brauner wrote: > This adds a stress test that should hopefully help us catch regressions > for [1], [2], and [3]. > > [1]: 2669b8b0c798 ("binder: prevent UAF for binderfs devices") > [2]: f0fe2c0f050d ("binder: prevent UAF for binderfs devices II") > [3]: 211b64e4b5b6 ("binderfs: use refcount for binder control devices too") > Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Do you care about 80-char line limits? (Or does the selftest tree? There are a few in here...) Otherwise, seems reasonable: Reviewed-by: Kees Cook <keescook@chromium.org> -Kees > --- > .../selftests/filesystems/binderfs/Makefile | 2 +- > .../filesystems/binderfs/binderfs_test.c | 416 ++++++++++++++---- > 2 files changed, 325 insertions(+), 93 deletions(-) > > diff --git a/tools/testing/selftests/filesystems/binderfs/Makefile b/tools/testing/selftests/filesystems/binderfs/Makefile > index 75315d9ba7a9..8af25ae96049 100644 > --- a/tools/testing/selftests/filesystems/binderfs/Makefile > +++ b/tools/testing/selftests/filesystems/binderfs/Makefile > @@ -1,6 +1,6 @@ > # 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 > diff --git a/tools/testing/selftests/filesystems/binderfs/binderfs_test.c b/tools/testing/selftests/filesystems/binderfs/binderfs_test.c > index d03ed8eed5eb..313ffad15614 100644 > --- a/tools/testing/selftests/filesystems/binderfs/binderfs_test.c > +++ b/tools/testing/selftests/filesystems/binderfs/binderfs_test.c > @@ -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; > -} > +#define PTR_TO_INT(p) ((int)((intptr_t)(p))) > +#define INT_TO_PTR(u) ((void *)((intptr_t)(u))) > > -static void write_to_file(const char *filename, const void *buf, size_t count, > - int allowed_errno) > -{ > - int fd, saved_errno; > - ssize_t ret; > - > - 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; > - } > - > - goto on_error; > +#define close_prot_errno_disarm(fd) \ > + if (fd >= 0) { \ > + int _e_ = errno; \ > + close(fd); \ > + errno = _e_; \ > + fd = -EBADF; \ > } > > - if ((size_t)ret != count) > - goto on_error; > - > - close(fd); > - return; > - > -on_error: > - saved_errno = errno; > - close(fd); > - errno = saved_errno; > - > - if (ret < 0) > - ksft_exit_fail_msg("%s - Failed to write to file %s\n", > - strerror(errno), filename); > +#define log_exit(format, ...) \ > + ({ \ > + fprintf(stderr, format "\n", ##__VA_ARGS__); \ > + exit(EXIT_FAILURE); \ > + }) > > - 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; > > @@ -143,7 +74,7 @@ static void __do_binderfs_test(void) > struct binderfs_device device = { 0 }; > struct binder_version version = { 0 }; > > - change_to_mountns(); > + change_mountns(); > > ret = mkdir("/dev/binderfs", 0755); > if (ret < 0) { > @@ -254,6 +185,283 @@ static void __do_binderfs_test(void) > ksft_inc_pass_cnt(); > } > > +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 }; > + > + 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(); > + > + ret = mkdir("/tmp/binderfs", 0755); > + if (ret < 0 && errno != EEXIST) > + log_exit("%s - Failed to create binderfs mountpoint\n", strerror(errno)); > + > + ret = mount(NULL, "/tmp/binderfs", "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++) { > + char path[4096]; > + > + fd = open("/tmp/binderfs/binder-control", 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(path, sizeof(path), "/tmp/binderfs/%d", i); > + fds[i] = open(path, O_RDONLY | O_CLOEXEC); > + if (fds[i] < 0) > + log_exit("%s - Failed to open binder device\n", strerror(errno)); > + } > + > + ret = umount2("/tmp/binderfs", MNT_DETACH); > + 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) > @@ -264,8 +472,32 @@ TEST(binderfs_test_privileged) > > TEST(binderfs_test_unprivileged) > { > - change_to_userns(); > - __do_binderfs_test(); > + 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); > + __do_binderfs_test(); > + exit(EXIT_SUCCESS); > + } > + > + change_idmaps(syncfds, pid); > + > + ret = wait_for_pid(pid); > + if (ret) > + ksft_exit_fail_msg("wait_for_pid() failed"); > } > > TEST_HARNESS_MAIN > -- > 2.25.1 >
On Thu, Mar 12, 2020 at 04:53:17PM -0700, Kees Cook wrote: > On Thu, Mar 12, 2020 at 02:15:30PM +0100, Christian Brauner wrote: > > This adds a stress test that should hopefully help us catch regressions > > for [1], [2], and [3]. > > > > [1]: 2669b8b0c798 ("binder: prevent UAF for binderfs devices") > > [2]: f0fe2c0f050d ("binder: prevent UAF for binderfs devices II") > > [3]: 211b64e4b5b6 ("binderfs: use refcount for binder control devices too") > > Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> > > Do you care about 80-char line limits? (Or does the selftest tree? There > are a few in here...) They should mostly all be calls to kselftest print functions. I usually never wrap them in tests so it's easy to do: git grep "Find me this error string" which becames annoying when you wrap them. :)
diff --git a/tools/testing/selftests/filesystems/binderfs/Makefile b/tools/testing/selftests/filesystems/binderfs/Makefile index 75315d9ba7a9..8af25ae96049 100644 --- a/tools/testing/selftests/filesystems/binderfs/Makefile +++ b/tools/testing/selftests/filesystems/binderfs/Makefile @@ -1,6 +1,6 @@ # 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 diff --git a/tools/testing/selftests/filesystems/binderfs/binderfs_test.c b/tools/testing/selftests/filesystems/binderfs/binderfs_test.c index d03ed8eed5eb..313ffad15614 100644 --- a/tools/testing/selftests/filesystems/binderfs/binderfs_test.c +++ b/tools/testing/selftests/filesystems/binderfs/binderfs_test.c @@ -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; -} +#define PTR_TO_INT(p) ((int)((intptr_t)(p))) +#define INT_TO_PTR(u) ((void *)((intptr_t)(u))) -static void write_to_file(const char *filename, const void *buf, size_t count, - int allowed_errno) -{ - int fd, saved_errno; - ssize_t ret; - - 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; - } - - goto on_error; +#define close_prot_errno_disarm(fd) \ + if (fd >= 0) { \ + int _e_ = errno; \ + close(fd); \ + errno = _e_; \ + fd = -EBADF; \ } - if ((size_t)ret != count) - goto on_error; - - close(fd); - return; - -on_error: - saved_errno = errno; - close(fd); - errno = saved_errno; - - if (ret < 0) - ksft_exit_fail_msg("%s - Failed to write to file %s\n", - strerror(errno), filename); +#define log_exit(format, ...) \ + ({ \ + fprintf(stderr, format "\n", ##__VA_ARGS__); \ + exit(EXIT_FAILURE); \ + }) - 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; @@ -143,7 +74,7 @@ static void __do_binderfs_test(void) struct binderfs_device device = { 0 }; struct binder_version version = { 0 }; - change_to_mountns(); + change_mountns(); ret = mkdir("/dev/binderfs", 0755); if (ret < 0) { @@ -254,6 +185,283 @@ static void __do_binderfs_test(void) ksft_inc_pass_cnt(); } +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 }; + + 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(); + + ret = mkdir("/tmp/binderfs", 0755); + if (ret < 0 && errno != EEXIST) + log_exit("%s - Failed to create binderfs mountpoint\n", strerror(errno)); + + ret = mount(NULL, "/tmp/binderfs", "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++) { + char path[4096]; + + fd = open("/tmp/binderfs/binder-control", 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(path, sizeof(path), "/tmp/binderfs/%d", i); + fds[i] = open(path, O_RDONLY | O_CLOEXEC); + if (fds[i] < 0) + log_exit("%s - Failed to open binder device\n", strerror(errno)); + } + + ret = umount2("/tmp/binderfs", MNT_DETACH); + 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) @@ -264,8 +472,32 @@ TEST(binderfs_test_privileged) TEST(binderfs_test_unprivileged) { - change_to_userns(); - __do_binderfs_test(); + 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); + __do_binderfs_test(); + exit(EXIT_SUCCESS); + } + + change_idmaps(syncfds, pid); + + ret = wait_for_pid(pid); + if (ret) + ksft_exit_fail_msg("wait_for_pid() failed"); } TEST_HARNESS_MAIN
This adds a stress test that should hopefully help us catch regressions for [1], [2], and [3]. [1]: 2669b8b0c798 ("binder: prevent UAF for binderfs devices") [2]: f0fe2c0f050d ("binder: prevent UAF for binderfs devices II") [3]: 211b64e4b5b6 ("binderfs: use refcount for binder control devices too") Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> --- .../selftests/filesystems/binderfs/Makefile | 2 +- .../filesystems/binderfs/binderfs_test.c | 416 ++++++++++++++---- 2 files changed, 325 insertions(+), 93 deletions(-)