This adds a selftest for `bpf_task_freeze_cgroup` kfunc. The test works by forking a child then:
1. Child: - Migrate to a new cgroup - Loads bpf programs - Trigger the 'lsm_freeze_cgroup' bpf program so it freeze itself. by calling "bpf_task_freeze_cgroup(child, 1)"
<- wait for parent to unthaw
- On unthaw it continues, forks another process and triggers the 'tp_newchild' bpf program to set some monitored pids of the new process, that are asserted at user space, to ensure that we resumed correctly.
2. Parent: - Keeps reading the 'cgroup.freeze' file of the child cgroup until it prints 1 which means the child cgroup is frozen - Attaches the sample 'lsm_task_free' so it triggers the bpf program and then calls "bpf_task_freeze_cgroup(task, 0);" on the child task to unthaw its cgroup. - Then waits for a clean exit of the child process.
The scenario allows to test both: freeze and unthaw a task cgroup.
Signed-off-by: Djalal Harouni tixxdz@gmail.com --- .../bpf/prog_tests/task_freeze_cgroup.c | 165 ++++++++++++++++++ .../bpf/progs/test_task_freeze_cgroup.c | 110 ++++++++++++ 2 files changed, 275 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/task_freeze_cgroup.c create mode 100644 tools/testing/selftests/bpf/progs/test_task_freeze_cgroup.c
diff --git a/tools/testing/selftests/bpf/prog_tests/task_freeze_cgroup.c b/tools/testing/selftests/bpf/prog_tests/task_freeze_cgroup.c new file mode 100644 index 000000000000..afb7d46194c5 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/task_freeze_cgroup.c @@ -0,0 +1,165 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2024 Isovalent */ + +#include <sys/syscall.h> +#include <test_progs.h> +#include <cgroup_helpers.h> +#include <unistd.h> +#include "test_task_freeze_cgroup.skel.h" + +#define FOO "/test-task-freeze-cgroup" + +static int bpf_sleepable(struct test_task_freeze_cgroup *skel) +{ + int err, foo; + pid_t pid; + + foo = test__join_cgroup(FOO); + if (!ASSERT_OK(foo < 0, "cgroup_join_foo")) + return -errno; + + skel = test_task_freeze_cgroup__open(); + if (!ASSERT_OK_PTR(skel, "test_task_freeze_cgroup__open")) + return -errno; + + skel->rodata->parent_pid = getppid(); + skel->rodata->monitor_pid = getpid(); + skel->rodata->cgid = get_cgroup_id(FOO); + skel->bss->new_pid = getpid(); + skel->bss->freeze = 1; + + err = test_task_freeze_cgroup__load(skel); + if (!ASSERT_OK(err, "test_task_freeze_cgroup__load")) + goto cleanup; + + /* First, attach the LSM program, and then it will be triggered when the + * TP_BTF program is attached. + */ + skel->links.lsm_freeze_cgroup = + bpf_program__attach_lsm(skel->progs.lsm_freeze_cgroup); + if (!ASSERT_OK_PTR(skel->links.lsm_freeze_cgroup, "attach_lsm")) { + err = -errno; + goto cleanup; + } + + /* This will fail */ + skel->links.tp_newchild = + bpf_program__attach_trace(skel->progs.tp_newchild); + if (!ASSERT_EQ(errno, EPERM, "attach_trace")) { + err = -EINVAL; + goto cleanup; + } + + /* Try again now */ + skel->links.tp_newchild = + bpf_program__attach_trace(skel->progs.tp_newchild); + if (!ASSERT_OK_PTR(skel->links.tp_newchild, "attach_trace")) { + err = -EINVAL; + goto cleanup; + } + + /* Trigger a new child and assert unfrozen state */ + pid = fork(); + if (pid == 0) + exit(0); + + err = (pid == -1); + if (ASSERT_OK(err, "fork process")) + wait(NULL); + + /* Now we should continue, assert that new_pid reflects child */ + ASSERT_NEQ(skel->rodata->monitor_pid, skel->bss->new_pid, + "test task_freeze_cgroup failed at monitor_pid != new_pid"); + ASSERT_NEQ(0, skel->bss->new_pid, + "test task_freeze_cgroup failed at remote_pid != 0"); + + /* Assert that bpf set new_pid to new forked child pid */ + ASSERT_EQ(pid, skel->bss->new_pid, + "test task_freeze_cgroup failed at pid == new_pid"); + + test_task_freeze_cgroup__detach(skel); + +cleanup: + test_task_freeze_cgroup__destroy(skel); + close(foo); + return err; +} + +void test_task_freeze_cgroup(void) +{ + pid_t pid, result; + char buf[512] = {0}; + char path[PATH_MAX] = {0}; + int ret, status, attempts, frozen = 0; + struct test_task_freeze_cgroup *skel = NULL; + + pid = fork(); + ret = (pid == -1); + if (!ASSERT_OK(ret, "fork process")) + return; + + if (pid == 0) { + ret = bpf_sleepable(skel); + ASSERT_EQ(0, ret, "bpf_sleepable failed"); + exit(ret); + } + + skel = test_task_freeze_cgroup__open(); + if (!ASSERT_OK_PTR(skel, "test_task_freeze_cgroup__open")) + goto out; + + snprintf(path, sizeof(path), + "/sys/fs/cgroup/cgroup-test-work-dir%d%s/cgroup.freeze", + pid, FOO); + + for (attempts = 5; attempts >= 0; attempts--) { + ret = 0; + int fd = open(path, O_RDONLY); + if (fd > 0) + ret = read(fd, buf, sizeof(buf) - 1); + if (ret > 0) { + errno = 0; + frozen = strtol(buf, NULL, 10); + if (errno) + frozen = 0; + } + + close(fd); + if (frozen) + break; + sleep(1); + } + + /* Assert that child cgroup is frozen */ + if (!ASSERT_EQ(1, frozen, "child cgroup not frozen")) + goto out; + + ret = test_task_freeze_cgroup__load(skel); + if (!ASSERT_OK(ret, "test_task_freeze_cgroup__load")) + goto out; + + /* Unthaw child cgroup from parent */ + skel->links.lsm_task_free = + bpf_program__attach_lsm(skel->progs.lsm_task_free); + if (!ASSERT_OK_PTR(skel->links.lsm_task_free, "attach_lsm")) + goto out; + + result = waitpid(pid, &status, WUNTRACED); + if (!ASSERT_NEQ(result, -1, "waitpid")) + goto detach; + + result = WIFEXITED(status); + if (!ASSERT_EQ(result, 1, "forked process did not terminate normally")) + goto detach; + + result = WEXITSTATUS(status); + if (!ASSERT_EQ(result, 0, "forked process did not exit successfully")) + goto detach; + +detach: + test_task_freeze_cgroup__detach(skel); + +out: + if (skel) + test_task_freeze_cgroup__destroy(skel); +} diff --git a/tools/testing/selftests/bpf/progs/test_task_freeze_cgroup.c b/tools/testing/selftests/bpf/progs/test_task_freeze_cgroup.c new file mode 100644 index 000000000000..dbd2d60f464e --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_task_freeze_cgroup.c @@ -0,0 +1,110 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2024 Isovalent */ + +#include <vmlinux.h> +#include <bpf/bpf_tracing.h> +#include <bpf/bpf_helpers.h> +#include <errno.h> +#include "bpf_misc.h" + +struct cgroup *bpf_cgroup_from_id(u64 cgid) __ksym; +long bpf_task_under_cgroup(struct task_struct *task, struct cgroup *ancestor) __ksym; +void bpf_cgroup_release(struct cgroup *p) __ksym; +struct task_struct *bpf_task_from_pid(s32 pid) __ksym; +struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym; +void bpf_task_release(struct task_struct *p) __ksym; + +int bpf_task_freeze_cgroup(struct task_struct *task, int freeze) __ksym; + +const volatile int parent_pid; +const volatile int monitor_pid; +const volatile __u64 cgid; +int new_pid; +int freeze; + +SEC("tp_btf/task_newtask") +int BPF_PROG(tp_newchild, struct task_struct *task, u64 clone_flags) +{ + struct cgroup *cgrp = NULL; + struct task_struct *acquired; + + if (monitor_pid != (bpf_get_current_pid_tgid() >> 32)) + return 0; + + acquired = bpf_task_acquire(task); + if (!acquired) + return 0; + + cgrp = bpf_cgroup_from_id(cgid); + if (!cgrp) + goto out; + + if (bpf_task_under_cgroup(acquired, cgrp)) + new_pid = acquired->tgid; + +out: + if (cgrp) + bpf_cgroup_release(cgrp); + bpf_task_release(acquired); + + return 0; +} + +/* This is attached from parent to trigger the bpf lsm hook, so parent + * can unthaw the child. + */ +SEC("lsm/task_free") +int BPF_PROG(lsm_task_free, struct task_struct *task) +{ + return 0; +} + +SEC("lsm.s/bpf") +int BPF_PROG(lsm_freeze_cgroup, int cmd, union bpf_attr *attr, unsigned int size) +{ + int ret = 0; + struct cgroup *cgrp = NULL; + struct task_struct *task; + + if (cmd != BPF_LINK_CREATE) + return ret; + + task = bpf_get_current_task_btf(); + if (parent_pid == task->pid) { + /* Unthaw child from parent */ + task = bpf_task_from_pid(monitor_pid); + if (!task) + return -ENOENT; + + ret = bpf_task_freeze_cgroup(task, 0); + bpf_task_release(task); + return ret; + } + + if (monitor_pid != task->pid) + return 0; + + /* Freeze the child cgroup from its context */ + cgrp = bpf_cgroup_from_id(cgid); + if (!cgrp) + goto out; + + if (!bpf_task_under_cgroup(task, cgrp)) + goto out; + + if (freeze) { + /* Schedule freeze task and return -EPERM */ + ret = bpf_task_freeze_cgroup(task, 1); + if (!ret) { + ret = -EPERM; + /* reset for next call */ + freeze = 0; + } + } +out: + if (cgrp) + bpf_cgroup_release(cgrp); + return ret; +} + +char _license[] SEC("license") = "GPL";