This adds a selftest for `bpf_cgroup_write_interface` 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.
<- 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 assert that the user space 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
to unthaw the child task cgroup.
- Then waits for a clean exit of the child process.
The scenario allows to test multiple sides of: freeze and unthaw a cgroup.
Signed-off-by: Djalal Harouni <tixxdz@xxxxxxxxx>
---
.../bpf/prog_tests/task_freeze_cgroup.c | 172 ++++++++++++++++++
.../bpf/progs/test_task_freeze_cgroup.c | 155 ++++++++++++++++
2 files changed, 327 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..d4e9c0f32196
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/task_freeze_cgroup.c
@@ -0,0 +1,172 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <sys/syscall.h>
+#include <test_progs.h>
+#include <cgroup_helpers.h>
+#include <unistd.h>
+#include "test_task_freeze_cgroup.skel.h"
+
+#define CGROUP_PATH "/test-task-freeze-cgroup"
+
+static int bpf_sleepable(struct test_task_freeze_cgroup *skel)
+{
+ int err, cgroup_fd;
+ pid_t new_pid2;
+
+ cgroup_fd = cgroup_setup_and_join(CGROUP_PATH);
+ if (!ASSERT_OK(cgroup_fd < 0, "cgroup_setup_and_join"))
+ return -errno;
+
+ skel = test_task_freeze_cgroup__open();
+ if (!ASSERT_OK_PTR(skel, "test_task_freeze_cgroup__open")) {
+ err = -errno;
+ goto cleanup_cgroup;
+ }
+
+ skel->rodata->parent_pid = getppid();
+ skel->rodata->monitor_pid = getpid();
+ skel->rodata->cgid = get_cgroup_id(CGROUP_PATH);
+ 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")) {
+ err = -errno;
+ goto cleanup_skel;
+ }
+
+ /* First attach the LSM Program that is triggered on bpf() calls
+ * especially on TP_BTF programs when 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_detach;
+ }
+
+ /* Attaching this must fail with -EPERM and freeze current task */
+ skel->links.tp_newchild =
+ bpf_program__attach_trace(skel->progs.tp_newchild);
+ if (!ASSERT_EQ(errno, EPERM, "attach_trace() must fail here")) {
+ err = -EINVAL;
+ goto cleanup_detach;
+ }
+
+ /* Continue */
+
+ /* Attach again now with success */
+ 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_detach;
+ }
+
+ /* Fork, update vars from BPF and assert the unfrozen state */
+ new_pid2 = fork();
+ if (new_pid2 == 0)
+ exit(0);
+
+ err = (new_pid2 == -1);
+ if (ASSERT_OK(err, "fork process"))
+ wait(NULL);
+
+ /* Now assert that new_pid2 reflects this new child */
+ ASSERT_NEQ(0, skel->bss->new_pid,
+ "test task_freeze_cgroup failed at new_pid != 0");
+ ASSERT_NEQ(skel->rodata->monitor_pid, skel->bss->new_pid,
+ "test task_freeze_cgroup failed at old monitor_pid != new_pid");
+ /* Assert that bpf sets new_pid to new forked child new_pid2 */
+ ASSERT_EQ(skel->bss->new_pid, new_pid2,
+ "test task_freeze_cgroup failed first child new_pid == new_pid2");
+
+cleanup_detach:
+ test_task_freeze_cgroup__detach(skel);
+cleanup_skel:
+ test_task_freeze_cgroup__destroy(skel);
+cleanup_cgroup:
+ close(cgroup_fd);
+ cleanup_cgroup_environment();
+ 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, fd;
+ 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, "child 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, CGROUP_PATH);
+
+ for (attempts = 10; attempts >= 0; attempts--) {
+ ret = 0;
+
+ 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;
+
+ /* Trigger the 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..07b4b65abc36
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_task_freeze_cgroup.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <vmlinux.h>
+#include <linux/types.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+#include <errno.h>
+#include "bpf_kfuncs.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;
+
+extern int bpf_cgroup_write_interface(struct cgroup *cgrp,
+ const char *name__str,
+ const struct bpf_dynptr *value_p,
+ loff_t off) __ksym __weak;
+
+char freeze_val[] = "1";
+char unthaw_val[] = "0";
+
+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;
+
+ /* Update new_pid with current pid */
+ if (bpf_task_under_cgroup(acquired, cgrp))
+ new_pid = acquired->tgid;
+
+out:
+ if (cgrp)
+ bpf_cgroup_release(cgrp);
+ bpf_task_release(acquired);
+
+ return 0;
+}
+
+/* Try to attach from parent to trigger the bpf lsm hook, so from
+ * parent context we unthaw child cgroup.
+ */
+SEC("lsm/task_free")
+int BPF_PROG(lsm_task_free, struct task_struct *task)
+{
+ return 0;
+}
+
+static int process_freeze_cgroup(int pid, int freeze)
+{
+ int ret = 0;
+ struct task_struct *task;
+ struct bpf_dynptr dyn_ptr;
+ struct cgroup *cgrp = NULL;
+
+ task = bpf_task_from_pid(pid);
+ if (!task)
+ return -EINVAL;
+
+ cgrp = bpf_cgroup_from_id(cgid);
+ if (!cgrp) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ if (!bpf_task_under_cgroup(task, cgrp))
+ goto out;
+
+ if (freeze)
+ bpf_dynptr_from_mem(freeze_val, sizeof(freeze_val), 0, &dyn_ptr);
+ else
+ bpf_dynptr_from_mem(unthaw_val, sizeof(unthaw_val), 0, &dyn_ptr);
+
+ ret = bpf_cgroup_write_interface(cgrp, "cgroup.freeze", &dyn_ptr, 0);
+
+out:
+ if (cgrp)
+ bpf_cgroup_release(cgrp);
+ bpf_task_release(task);
+ return ret;
+}
+
+SEC("lsm.s/bpf")
+int BPF_PROG(lsm_freeze_cgroup, int cmd, union bpf_attr *attr, unsigned int size)
+{
+ int ret = 0;
+ struct task_struct *task;
+ struct cgroup *cgrp = NULL;
+
+ if (cmd != BPF_LINK_CREATE)
+ return 0;
+
+ task = bpf_get_current_task_btf();
+ if (parent_pid == task->pid) {
+ /* Parent context: unthaw child */
+ process_freeze_cgroup(monitor_pid, 0);
+ return 0;
+ }
+
+ /* Nothing todo */
+ if (!freeze)
+ return 0;
+
+ /* Child context */
+ if (monitor_pid != task->pid)
+ return 0;
+
+ /* Ensure we are under the corresponding cgroup so we freeze
+ * current child from its context
+ */
+ cgrp = bpf_cgroup_from_id(cgid);
+ if (!cgrp)
+ return 0;
+
+ if (!bpf_task_under_cgroup(task, cgrp))
+ goto out;
+
+ /* Schedule freeze task and return -EPERM */
+ ret = process_freeze_cgroup(monitor_pid, freeze);
+
+ /* On error or 0 we return zero and we catch at
+ * user space if the cgroup was not frozen.
+ */
+ ret = (ret > 0) ? -EPERM : 0;
+
+ /* Reset for next calls */
+ freeze = 0;
+out:
+ if (cgrp)
+ bpf_cgroup_release(cgrp);
+ return ret;
+}
+
+char _license[] SEC("license") = "GPL";
--
2.43.0
