diff options
author | KP Singh <kpsingh@google.com> | 2020-11-06 13:37:46 +0300 |
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committer | Alexei Starovoitov <ast@kernel.org> | 2020-11-06 19:08:38 +0300 |
commit | 9cde3beeadb311d4b435a7d28d5ab72bcc5de65d (patch) | |
tree | 89ba3159e7b5be9c9a4ba0e1ff139fefbd6b3e97 /tools/testing/selftests/bpf/prog_tests/test_local_storage.c | |
parent | a367efa71b3f5a53281ca9772f8bf43166dfdf5f (diff) | |
download | linux-9cde3beeadb311d4b435a7d28d5ab72bcc5de65d.tar.xz |
bpf: Add tests for task_local_storage
The test exercises the syscall based map operations by creating a pidfd
for the current process.
For verifying kernel / LSM functionality, the test implements a simple
MAC policy which denies an executable from unlinking itself. The LSM
program bprm_committed_creds sets a task_local_storage with a pointer to
the inode. This is then used to detect if the task is trying to unlink
itself in the inode_unlink LSM hook.
The test copies /bin/rm to /tmp and executes it in a child thread with
the intention of deleting itself. A successful test should prevent the
the running executable from deleting itself.
The bpf programs are also updated to call bpf_spin_{lock, unlock} to
trigger the verfier checks for spin locks.
The temporary file is cleaned up later in the test.
Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20201106103747.2780972-9-kpsingh@chromium.org
Diffstat (limited to 'tools/testing/selftests/bpf/prog_tests/test_local_storage.c')
-rw-r--r-- | tools/testing/selftests/bpf/prog_tests/test_local_storage.c | 185 |
1 files changed, 172 insertions, 13 deletions
diff --git a/tools/testing/selftests/bpf/prog_tests/test_local_storage.c b/tools/testing/selftests/bpf/prog_tests/test_local_storage.c index 91cd6f357246..4e7f6a4965f2 100644 --- a/tools/testing/selftests/bpf/prog_tests/test_local_storage.c +++ b/tools/testing/selftests/bpf/prog_tests/test_local_storage.c @@ -4,30 +4,161 @@ * Copyright (C) 2020 Google LLC. */ +#include <asm-generic/errno-base.h> +#include <sys/stat.h> #include <test_progs.h> #include <linux/limits.h> #include "local_storage.skel.h" #include "network_helpers.h" -int create_and_unlink_file(void) +static inline int sys_pidfd_open(pid_t pid, unsigned int flags) { - char fname[PATH_MAX] = "/tmp/fileXXXXXX"; - int fd; + return syscall(__NR_pidfd_open, pid, flags); +} + +static inline ssize_t copy_file_range(int fd_in, loff_t *off_in, int fd_out, + loff_t *off_out, size_t len, + unsigned int flags) +{ + return syscall(__NR_copy_file_range, fd_in, off_in, fd_out, off_out, + len, flags); +} + +static unsigned int duration; + +#define TEST_STORAGE_VALUE 0xbeefdead - fd = mkstemp(fname); - if (fd < 0) - return fd; +struct storage { + void *inode; + unsigned int value; + /* Lock ensures that spin locked versions of local stoage operations + * also work, most operations in this tests are still single threaded + */ + struct bpf_spin_lock lock; +}; + +/* Copies an rm binary to a temp file. dest is a mkstemp template */ +static int copy_rm(char *dest) +{ + int fd_in, fd_out = -1, ret = 0; + struct stat stat; + + fd_in = open("/bin/rm", O_RDONLY); + if (fd_in < 0) + return -errno; + + fd_out = mkstemp(dest); + if (fd_out < 0) { + ret = -errno; + goto out; + } + + ret = fstat(fd_in, &stat); + if (ret == -1) { + ret = -errno; + goto out; + } + + ret = copy_file_range(fd_in, NULL, fd_out, NULL, stat.st_size, 0); + if (ret == -1) { + ret = -errno; + goto out; + } + + /* Set executable permission on the copied file */ + ret = chmod(dest, 0100); + if (ret == -1) + ret = -errno; + +out: + close(fd_in); + close(fd_out); + return ret; +} + +/* Fork and exec the provided rm binary and return the exit code of the + * forked process and its pid. + */ +static int run_self_unlink(int *monitored_pid, const char *rm_path) +{ + int child_pid, child_status, ret; + int null_fd; + + child_pid = fork(); + if (child_pid == 0) { + null_fd = open("/dev/null", O_WRONLY); + dup2(null_fd, STDOUT_FILENO); + dup2(null_fd, STDERR_FILENO); + close(null_fd); + + *monitored_pid = getpid(); + /* Use the copied /usr/bin/rm to delete itself + * /tmp/copy_of_rm /tmp/copy_of_rm. + */ + ret = execlp(rm_path, rm_path, rm_path, NULL); + if (ret) + exit(errno); + } else if (child_pid > 0) { + waitpid(child_pid, &child_status, 0); + return WEXITSTATUS(child_status); + } + + return -EINVAL; +} - close(fd); - unlink(fname); - return 0; +static bool check_syscall_operations(int map_fd, int obj_fd) +{ + struct storage val = { .value = TEST_STORAGE_VALUE, .lock = { 0 } }, + lookup_val = { .value = 0, .lock = { 0 } }; + int err; + + /* Looking up an existing element should fail initially */ + err = bpf_map_lookup_elem_flags(map_fd, &obj_fd, &lookup_val, + BPF_F_LOCK); + if (CHECK(!err || errno != ENOENT, "bpf_map_lookup_elem", + "err:%d errno:%d\n", err, errno)) + return false; + + /* Create a new element */ + err = bpf_map_update_elem(map_fd, &obj_fd, &val, + BPF_NOEXIST | BPF_F_LOCK); + if (CHECK(err < 0, "bpf_map_update_elem", "err:%d errno:%d\n", err, + errno)) + return false; + + /* Lookup the newly created element */ + err = bpf_map_lookup_elem_flags(map_fd, &obj_fd, &lookup_val, + BPF_F_LOCK); + if (CHECK(err < 0, "bpf_map_lookup_elem", "err:%d errno:%d", err, + errno)) + return false; + + /* Check the value of the newly created element */ + if (CHECK(lookup_val.value != val.value, "bpf_map_lookup_elem", + "value got = %x errno:%d", lookup_val.value, val.value)) + return false; + + err = bpf_map_delete_elem(map_fd, &obj_fd); + if (CHECK(err, "bpf_map_delete_elem()", "err:%d errno:%d\n", err, + errno)) + return false; + + /* The lookup should fail, now that the element has been deleted */ + err = bpf_map_lookup_elem_flags(map_fd, &obj_fd, &lookup_val, + BPF_F_LOCK); + if (CHECK(!err || errno != ENOENT, "bpf_map_lookup_elem", + "err:%d errno:%d\n", err, errno)) + return false; + + return true; } void test_test_local_storage(void) { + char tmp_exec_path[PATH_MAX] = "/tmp/copy_of_rmXXXXXX"; + int err, serv_sk = -1, task_fd = -1; struct local_storage *skel = NULL; - int err, duration = 0, serv_sk = -1; skel = local_storage__open_and_load(); if (CHECK(!skel, "skel_load", "lsm skeleton failed\n")) @@ -37,12 +168,37 @@ void test_test_local_storage(void) if (CHECK(err, "attach", "lsm attach failed: %d\n", err)) goto close_prog; - skel->bss->monitored_pid = getpid(); + task_fd = sys_pidfd_open(getpid(), 0); + if (CHECK(task_fd < 0, "pidfd_open", + "failed to get pidfd err:%d, errno:%d", task_fd, errno)) + goto close_prog; - err = create_and_unlink_file(); - if (CHECK(err < 0, "exec_cmd", "err %d errno %d\n", err, errno)) + if (!check_syscall_operations(bpf_map__fd(skel->maps.task_storage_map), + task_fd)) goto close_prog; + err = copy_rm(tmp_exec_path); + if (CHECK(err < 0, "copy_rm", "err %d errno %d\n", err, errno)) + goto close_prog; + + /* Sets skel->bss->monitored_pid to the pid of the forked child + * forks a child process that executes tmp_exec_path and tries to + * unlink its executable. This operation should be denied by the loaded + * LSM program. + */ + err = run_self_unlink(&skel->bss->monitored_pid, tmp_exec_path); + if (CHECK(err != EPERM, "run_self_unlink", "err %d want EPERM\n", err)) + goto close_prog_unlink; + + /* Set the process being monitored to be the current process */ + skel->bss->monitored_pid = getpid(); + + /* Remove the temporary created executable */ + err = unlink(tmp_exec_path); + if (CHECK(err != 0, "unlink", "unable to unlink %s: %d", tmp_exec_path, + errno)) + goto close_prog_unlink; + CHECK(skel->data->inode_storage_result != 0, "inode_storage_result", "inode_local_storage not set\n"); @@ -55,6 +211,9 @@ void test_test_local_storage(void) close(serv_sk); +close_prog_unlink: + unlink(tmp_exec_path); close_prog: + close(task_fd); local_storage__destroy(skel); } |