It was found in [1] that bpf_inode_storage_get helper did not check the nullness of the passed owner ptr which caused an oops when dereferenced. This change incorporates the example suggested in [1] into the local storage selftest. The test is updated to create a temporary directory instead of just using a tempfile. In order to replicate the issue this copied rm binary is renamed tiggering the inode_rename with a null pointer for the new_inode. The logic to verify the setting and deletion of the inode local storage of the old inode is also moved to this LSM hook. The change also removes the copy_rm function and simply shells out to copy files and recursively delete directories and consolidates the logic of setting the initial inode storage to the bprm_committed_creds hook and removes the file_open hook. [1]: https://lore.kernel.org/bpf/CANaYP3HWkH91SN=wTNO9FL_2ztHfqcXKX38SSE-JJ2voh+vssw@xxxxxxxxxxxxxx Suggested-by: Gilad Reti <gilad.reti@xxxxxxxxx> Acked-by: Yonghong Song <yhs@xxxxxx> Signed-off-by: KP Singh <kpsingh@xxxxxxxxxx> --- .../bpf/prog_tests/test_local_storage.c | 96 +++++-------------- .../selftests/bpf/progs/local_storage.c | 62 ++++++------ 2 files changed, 61 insertions(+), 97 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 c0fe73a17ed1..3bfcf00c0a67 100644 --- a/tools/testing/selftests/bpf/prog_tests/test_local_storage.c +++ b/tools/testing/selftests/bpf/prog_tests/test_local_storage.c @@ -34,61 +34,6 @@ struct storage { 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; - char *buf = NULL; - - 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; - } - - buf = malloc(stat.st_blksize); - if (!buf) { - ret = -errno; - goto out; - } - - while (ret = read(fd_in, buf, stat.st_blksize), ret > 0) { - ret = write(fd_out, buf, ret); - if (ret < 0) { - ret = -errno; - goto out; - - } - } - if (ret < 0) { - ret = -errno; - goto out; - - } - - /* Set executable permission on the copied file */ - ret = chmod(dest, 0100); - if (ret == -1) - ret = -errno; - -out: - free(buf); - 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. */ @@ -168,9 +113,11 @@ static bool check_syscall_operations(int map_fd, int obj_fd) void test_test_local_storage(void) { - char tmp_exec_path[PATH_MAX] = "/tmp/copy_of_rmXXXXXX"; + char tmp_dir_path[64] = "/tmp/local_storageXXXXXX"; int err, serv_sk = -1, task_fd = -1, rm_fd = -1; struct local_storage *skel = NULL; + char tmp_exec_path[64]; + char cmd[256]; skel = local_storage__open_and_load(); if (CHECK(!skel, "skel_load", "lsm skeleton failed\n")) @@ -189,18 +136,24 @@ void test_test_local_storage(void) task_fd)) goto close_prog; - err = copy_rm(tmp_exec_path); - if (CHECK(err < 0, "copy_rm", "err %d errno %d\n", err, errno)) + if (CHECK(!mkdtemp(tmp_dir_path), "mkdtemp", + "unable to create tmpdir: %d\n", errno)) goto close_prog; + snprintf(tmp_exec_path, sizeof(tmp_exec_path), "%s/copy_of_rm", + tmp_dir_path); + snprintf(cmd, sizeof(cmd), "cp /bin/rm %s", tmp_exec_path); + if (CHECK_FAIL(system(cmd))) + goto close_prog_rmdir; + rm_fd = open(tmp_exec_path, O_RDONLY); if (CHECK(rm_fd < 0, "open", "failed to open %s err:%d, errno:%d", tmp_exec_path, rm_fd, errno)) - goto close_prog; + goto close_prog_rmdir; if (!check_syscall_operations(bpf_map__fd(skel->maps.inode_storage_map), rm_fd)) - goto close_prog; + goto close_prog_rmdir; /* Sets skel->bss->monitored_pid to the pid of the forked child * forks a child process that executes tmp_exec_path and tries to @@ -209,33 +162,36 @@ void test_test_local_storage(void) */ 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; + goto close_prog_rmdir; /* 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; + /* Move copy_of_rm to a new location so that it triggers the + * inode_rename LSM hook with a new_dentry that has a NULL inode ptr. + */ + snprintf(cmd, sizeof(cmd), "mv %s/copy_of_rm %s/check_null_ptr", + tmp_dir_path, tmp_dir_path); + if (CHECK_FAIL(system(cmd))) + goto close_prog_rmdir; CHECK(skel->data->inode_storage_result != 0, "inode_storage_result", "inode_local_storage not set\n"); serv_sk = start_server(AF_INET6, SOCK_STREAM, NULL, 0, 0); if (CHECK(serv_sk < 0, "start_server", "failed to start server\n")) - goto close_prog; + goto close_prog_rmdir; CHECK(skel->data->sk_storage_result != 0, "sk_storage_result", "sk_local_storage not set\n"); if (!check_syscall_operations(bpf_map__fd(skel->maps.sk_storage_map), serv_sk)) - goto close_prog; + goto close_prog_rmdir; -close_prog_unlink: - unlink(tmp_exec_path); +close_prog_rmdir: + snprintf(cmd, sizeof(cmd), "rm -rf %s", tmp_dir_path); + system(cmd); close_prog: close(serv_sk); close(rm_fd); diff --git a/tools/testing/selftests/bpf/progs/local_storage.c b/tools/testing/selftests/bpf/progs/local_storage.c index 3e3de130f28f..95868bc7ada9 100644 --- a/tools/testing/selftests/bpf/progs/local_storage.c +++ b/tools/testing/selftests/bpf/progs/local_storage.c @@ -50,7 +50,6 @@ int BPF_PROG(unlink_hook, struct inode *dir, struct dentry *victim) __u32 pid = bpf_get_current_pid_tgid() >> 32; struct local_storage *storage; bool is_self_unlink; - int err; if (pid != monitored_pid) return 0; @@ -66,8 +65,27 @@ int BPF_PROG(unlink_hook, struct inode *dir, struct dentry *victim) return -EPERM; } - storage = bpf_inode_storage_get(&inode_storage_map, victim->d_inode, 0, - BPF_LOCAL_STORAGE_GET_F_CREATE); + return 0; +} + +SEC("lsm/inode_rename") +int BPF_PROG(inode_rename, struct inode *old_dir, struct dentry *old_dentry, + struct inode *new_dir, struct dentry *new_dentry, + unsigned int flags) +{ + __u32 pid = bpf_get_current_pid_tgid() >> 32; + struct local_storage *storage; + int err; + + /* new_dentry->d_inode can be NULL when the inode is renamed to a file + * that did not exist before. The helper should be able to handle this + * NULL pointer. + */ + bpf_inode_storage_get(&inode_storage_map, new_dentry->d_inode, 0, + BPF_LOCAL_STORAGE_GET_F_CREATE); + + storage = bpf_inode_storage_get(&inode_storage_map, old_dentry->d_inode, + 0, 0); if (!storage) return 0; @@ -76,7 +94,7 @@ int BPF_PROG(unlink_hook, struct inode *dir, struct dentry *victim) inode_storage_result = -1; bpf_spin_unlock(&storage->lock); - err = bpf_inode_storage_delete(&inode_storage_map, victim->d_inode); + err = bpf_inode_storage_delete(&inode_storage_map, old_dentry->d_inode); if (!err) inode_storage_result = err; @@ -133,37 +151,18 @@ int BPF_PROG(socket_post_create, struct socket *sock, int family, int type, return 0; } -SEC("lsm/file_open") -int BPF_PROG(file_open, struct file *file) -{ - __u32 pid = bpf_get_current_pid_tgid() >> 32; - struct local_storage *storage; - - if (pid != monitored_pid) - return 0; - - if (!file->f_inode) - return 0; - - storage = bpf_inode_storage_get(&inode_storage_map, file->f_inode, 0, - BPF_LOCAL_STORAGE_GET_F_CREATE); - if (!storage) - return 0; - - bpf_spin_lock(&storage->lock); - storage->value = DUMMY_STORAGE_VALUE; - bpf_spin_unlock(&storage->lock); - return 0; -} - /* This uses the local storage to remember the inode of the binary that a * process was originally executing. */ SEC("lsm/bprm_committed_creds") void BPF_PROG(exec, struct linux_binprm *bprm) { + __u32 pid = bpf_get_current_pid_tgid() >> 32; struct local_storage *storage; + if (pid != monitored_pid) + return; + storage = bpf_task_storage_get(&task_storage_map, bpf_get_current_task_btf(), 0, BPF_LOCAL_STORAGE_GET_F_CREATE); @@ -172,4 +171,13 @@ void BPF_PROG(exec, struct linux_binprm *bprm) storage->exec_inode = bprm->file->f_inode; bpf_spin_unlock(&storage->lock); } + + storage = bpf_inode_storage_get(&inode_storage_map, bprm->file->f_inode, + 0, BPF_LOCAL_STORAGE_GET_F_CREATE); + if (!storage) + return; + + bpf_spin_lock(&storage->lock); + storage->value = DUMMY_STORAGE_VALUE; + bpf_spin_unlock(&storage->lock); } -- 2.30.0.284.gd98b1dd5eaa7-goog
