tools/testing/selftests/bpf/prog_tests/test_local_storage.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 /*
   4  * Copyright (C) 2020 Google LLC.
   5  */
   6
   7 #include <asm-generic/errno-base.h>
   8 #include <sys/stat.h>
   9 #include <test_progs.h>
  10 #include <linux/limits.h>
  11
  12 #include "local_storage.skel.h"
  13 #include "network_helpers.h"
  14
  15 #ifndef __NR_pidfd_open
  16 #define __NR_pidfd_open 434
  17 #endif
  18
  19 static inline int sys_pidfd_open(pid_t pid, unsigned int flags)
  20 {
  21         return syscall(__NR_pidfd_open, pid, flags);
  22 }
  23
  24 static unsigned int duration;
  25
  26 #define TEST_STORAGE_VALUE 0xbeefdead
  27
  28 struct storage {
  29         void *inode;
  30         unsigned int value;
  31         /* Lock ensures that spin locked versions of local stoage operations
  32          * also work, most operations in this tests are still single threaded
  33          */
  34         struct bpf_spin_lock lock;
  35 };
  36
  37 /* Copies an rm binary to a temp file. dest is a mkstemp template */
  38 static int copy_rm(char *dest)
  39 {
  40         int fd_in, fd_out = -1, ret = 0;
  41         struct stat stat;
  42         char *buf = NULL;
  43
  44         fd_in = open("/bin/rm", O_RDONLY);
  45         if (fd_in < 0)
  46                 return -errno;
  47
  48         fd_out = mkstemp(dest);
  49         if (fd_out < 0) {
  50                 ret = -errno;
  51                 goto out;
  52         }
  53
  54         ret = fstat(fd_in, &stat);
  55         if (ret == -1) {
  56                 ret = -errno;
  57                 goto out;
  58         }
  59
  60         buf = malloc(stat.st_blksize);
  61         if (!buf) {
  62                 ret = -errno;
  63                 goto out;
  64         }
  65
  66         while (ret = read(fd_in, buf, stat.st_blksize), ret > 0) {
  67                 ret = write(fd_out, buf, ret);
  68                 if (ret < 0) {
  69                         ret = -errno;
  70                         goto out;
  71
  72                 }
  73         }
  74         if (ret < 0) {
  75                 ret = -errno;
  76                 goto out;
  77
  78         }
  79
  80         /* Set executable permission on the copied file */
  81         ret = chmod(dest, 0100);
  82         if (ret == -1)
  83                 ret = -errno;
  84
  85 out:
  86         free(buf);
  87         close(fd_in);
  88         close(fd_out);
  89         return ret;
  90 }
  91
  92 /* Fork and exec the provided rm binary and return the exit code of the
  93  * forked process and its pid.
  94  */
  95 static int run_self_unlink(int *monitored_pid, const char *rm_path)
  96 {
  97         int child_pid, child_status, ret;
  98         int null_fd;
  99
 100         child_pid = fork();
 101         if (child_pid == 0) {
 102                 null_fd = open("/dev/null", O_WRONLY);
 103                 dup2(null_fd, STDOUT_FILENO);
 104                 dup2(null_fd, STDERR_FILENO);
 105                 close(null_fd);
 106
 107                 *monitored_pid = getpid();
 108                 /* Use the copied /usr/bin/rm to delete itself
 109                  * /tmp/copy_of_rm /tmp/copy_of_rm.
 110                  */
 111                 ret = execlp(rm_path, rm_path, rm_path, NULL);
 112                 if (ret)
 113                         exit(errno);
 114         } else if (child_pid > 0) {
 115                 waitpid(child_pid, &child_status, 0);
 116                 return WEXITSTATUS(child_status);
 117         }
 118
 119         return -EINVAL;
 120 }
 121
 122 static bool check_syscall_operations(int map_fd, int obj_fd)
 123 {
 124         struct storage val = { .value = TEST_STORAGE_VALUE, .lock = { 0 } },
 125                        lookup_val = { .value = 0, .lock = { 0 } };
 126         int err;
 127
 128         /* Looking up an existing element should fail initially */
 129         err = bpf_map_lookup_elem_flags(map_fd, &obj_fd, &lookup_val,
 130                                         BPF_F_LOCK);
 131         if (CHECK(!err || errno != ENOENT, "bpf_map_lookup_elem",
 132                   "err:%d errno:%d\n", err, errno))
 133                 return false;
 134
 135         /* Create a new element */
 136         err = bpf_map_update_elem(map_fd, &obj_fd, &val,
 137                                   BPF_NOEXIST | BPF_F_LOCK);
 138         if (CHECK(err < 0, "bpf_map_update_elem", "err:%d errno:%d\n", err,
 139                   errno))
 140                 return false;
 141
 142         /* Lookup the newly created element */
 143         err = bpf_map_lookup_elem_flags(map_fd, &obj_fd, &lookup_val,
 144                                         BPF_F_LOCK);
 145         if (CHECK(err < 0, "bpf_map_lookup_elem", "err:%d errno:%d", err,
 146                   errno))
 147                 return false;
 148
 149         /* Check the value of the newly created element */
 150         if (CHECK(lookup_val.value != val.value, "bpf_map_lookup_elem",
 151                   "value got = %x errno:%d", lookup_val.value, val.value))
 152                 return false;
 153
 154         err = bpf_map_delete_elem(map_fd, &obj_fd);
 155         if (CHECK(err, "bpf_map_delete_elem()", "err:%d errno:%d\n", err,
 156                   errno))
 157                 return false;
 158
 159         /* The lookup should fail, now that the element has been deleted */
 160         err = bpf_map_lookup_elem_flags(map_fd, &obj_fd, &lookup_val,
 161                                         BPF_F_LOCK);
 162         if (CHECK(!err || errno != ENOENT, "bpf_map_lookup_elem",
 163                   "err:%d errno:%d\n", err, errno))
 164                 return false;
 165
 166         return true;
 167 }
 168
 169 void test_test_local_storage(void)
 170 {
 171         char tmp_exec_path[PATH_MAX] = "/tmp/copy_of_rmXXXXXX";
 172         int err, serv_sk = -1, task_fd = -1, rm_fd = -1;
 173         struct local_storage *skel = NULL;
 174
 175         skel = local_storage__open_and_load();
 176         if (CHECK(!skel, "skel_load", "lsm skeleton failed\n"))
 177                 goto close_prog;
 178
 179         err = local_storage__attach(skel);
 180         if (CHECK(err, "attach", "lsm attach failed: %d\n", err))
 181                 goto close_prog;
 182
 183         task_fd = sys_pidfd_open(getpid(), 0);
 184         if (CHECK(task_fd < 0, "pidfd_open",
 185                   "failed to get pidfd err:%d, errno:%d", task_fd, errno))
 186                 goto close_prog;
 187
 188         if (!check_syscall_operations(bpf_map__fd(skel->maps.task_storage_map),
 189                                       task_fd))
 190                 goto close_prog;
 191
 192         err = copy_rm(tmp_exec_path);
 193         if (CHECK(err < 0, "copy_rm", "err %d errno %d\n", err, errno))
 194                 goto close_prog;
 195
 196         rm_fd = open(tmp_exec_path, O_RDONLY);
 197         if (CHECK(rm_fd < 0, "open", "failed to open %s err:%d, errno:%d",
 198                   tmp_exec_path, rm_fd, errno))
 199                 goto close_prog;
 200
 201         if (!check_syscall_operations(bpf_map__fd(skel->maps.inode_storage_map),
 202                                       rm_fd))
 203                 goto close_prog;
 204
 205         /* Sets skel->bss->monitored_pid to the pid of the forked child
 206          * forks a child process that executes tmp_exec_path and tries to
 207          * unlink its executable. This operation should be denied by the loaded
 208          * LSM program.
 209          */
 210         err = run_self_unlink(&skel->bss->monitored_pid, tmp_exec_path);
 211         if (CHECK(err != EPERM, "run_self_unlink", "err %d want EPERM\n", err))
 212                 goto close_prog_unlink;
 213
 214         /* Set the process being monitored to be the current process */
 215         skel->bss->monitored_pid = getpid();
 216
 217         /* Remove the temporary created executable */
 218         err = unlink(tmp_exec_path);
 219         if (CHECK(err != 0, "unlink", "unable to unlink %s: %d", tmp_exec_path,
 220                   errno))
 221                 goto close_prog_unlink;
 222
 223         CHECK(skel->data->inode_storage_result != 0, "inode_storage_result",
 224               "inode_local_storage not set\n");
 225
 226         serv_sk = start_server(AF_INET6, SOCK_STREAM, NULL, 0, 0);
 227         if (CHECK(serv_sk < 0, "start_server", "failed to start server\n"))
 228                 goto close_prog;
 229
 230         CHECK(skel->data->sk_storage_result != 0, "sk_storage_result",
 231               "sk_local_storage not set\n");
 232
 233         if (!check_syscall_operations(bpf_map__fd(skel->maps.sk_storage_map),
 234                                       serv_sk))
 235                 goto close_prog;
 236
 237 close_prog_unlink:
 238         unlink(tmp_exec_path);
 239 close_prog:
 240         close(serv_sk);
 241         close(rm_fd);
 242         close(task_fd);
 243         local_storage__destroy(skel);
 244 }