[PATCH bpf-next 1/2] bpf: Add bpf_task_from_vpid() kfunc

[PATCH bpf-next 1/2] bpf: Add bpf_task_from_vpid() kfunc

[Juntong Deng]

bpf_task_from_pid() that currently exists looks up the
struct task_struct corresponding to the pid in the root pid
namespace (init_pid_ns).

This patch adds bpf_task_from_vpid() which looks up the
struct task_struct corresponding to vpid in the pid namespace
of the current process.

This is useful for getting information about other processes
in the same pid namespace.

Signed-off-by: Juntong Deng <juntong.deng@outlook.com>
---
 kernel/bpf/helpers.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 4053f279ed4c..e977c12d60e1 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2521,6 +2521,25 @@ __bpf_kfunc struct task_struct *bpf_task_from_pid(s32 pid)
 	return p;
 }
 
+/**
+ * bpf_task_from_vpid - Find a struct task_struct from its vpid by looking it up
+ * in the pid namespace of the current task. If a task is returned, it must
+ * either be stored in a map, or released with bpf_task_release().
+ * @vpid: The vpid of the task being looked up.
+ */
+__bpf_kfunc struct task_struct *bpf_task_from_vpid(s32 vpid)
+{
+	struct task_struct *p;
+
+	rcu_read_lock();
+	p = find_task_by_vpid(vpid);
+	if (p)
+		p = bpf_task_acquire(p);
+	rcu_read_unlock();
+
+	return p;
+}
+
 /**
  * bpf_dynptr_slice() - Obtain a read-only pointer to the dynptr data.
  * @p: The dynptr whose data slice to retrieve
@@ -3034,6 +3053,7 @@ BTF_ID_FLAGS(func, bpf_task_under_cgroup, KF_RCU)
 BTF_ID_FLAGS(func, bpf_task_get_cgroup1, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
 #endif
 BTF_ID_FLAGS(func, bpf_task_from_pid, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_task_from_vpid, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_throw)
 BTF_KFUNCS_END(generic_btf_ids)
 
-- 
2.39.5

[PATCH bpf-next 2/2] selftests/bpf: Add tests for bpf_task_from_vpid() kfunc

[Juntong Deng]

This patch adds test cases for bpf_task_from_vpid() kfunc.

task_kfunc_from_vpid_no_null_check is used to test the case where
the return value is not checked for NULL pointer.

test_task_from_vpid_current is used to test obtaining the
struct task_struct of the process in the pid namespace based on vpid.

test_task_from_vpid_invalid is used to test the case of invalid vpid.

test_task_from_vpid_current and test_task_from_vpid_invalid will run
in the new namespace.

Signed-off-by: Juntong Deng <juntong.deng@outlook.com>
---
 .../selftests/bpf/prog_tests/task_kfunc.c     | 80 +++++++++++++++++++
 .../selftests/bpf/progs/task_kfunc_common.h   |  1 +
 .../selftests/bpf/progs/task_kfunc_failure.c  | 14 ++++
 .../selftests/bpf/progs/task_kfunc_success.c  | 51 ++++++++++++
 4 files changed, 146 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/task_kfunc.c b/tools/testing/selftests/bpf/prog_tests/task_kfunc.c
index d4579f735398..83b90335967a 100644
--- a/tools/testing/selftests/bpf/prog_tests/task_kfunc.c
+++ b/tools/testing/selftests/bpf/prog_tests/task_kfunc.c
@@ -68,6 +68,74 @@ static void run_success_test(const char *prog_name)
 	task_kfunc_success__destroy(skel);
 }
 
+static int run_vpid_test(void *prog_name)
+{
+	struct task_kfunc_success *skel;
+	struct bpf_program *prog;
+	int prog_fd, err = 0;
+
+	if (getpid() != 1)
+		return 1;
+
+	skel = open_load_task_kfunc_skel();
+	if (!skel)
+		return 2;
+
+	if (skel->bss->err) {
+		err = 3;
+		goto cleanup;
+	}
+
+	prog = bpf_object__find_program_by_name(skel->obj, prog_name);
+	if (!prog) {
+		err = 4;
+		goto cleanup;
+	}
+
+	prog_fd = bpf_program__fd(prog);
+	if (prog_fd < 0) {
+		err = 5;
+		goto cleanup;
+	}
+
+	if (bpf_prog_test_run_opts(prog_fd, NULL)) {
+		err = 6;
+		goto cleanup;
+	}
+
+	if (skel->bss->err)
+		err = 7 + skel->bss->err;
+cleanup:
+	task_kfunc_success__destroy(skel);
+	return err;
+}
+
+static void run_vpid_success_test(const char *prog_name)
+{
+	const int stack_size = 1024 * 1024;
+	int child_pid, wstatus;
+	char *stack;
+
+	stack = (char *)malloc(stack_size);
+	if (!ASSERT_OK_PTR(stack, "clone_stack"))
+		return;
+
+	child_pid = clone(run_vpid_test, stack + stack_size,
+			  CLONE_NEWPID | SIGCHLD, (void *)prog_name);
+	if (!ASSERT_GT(child_pid, -1, "child_pid"))
+		goto cleanup;
+
+	if (!ASSERT_GT(waitpid(child_pid, &wstatus, 0), -1, "waitpid"))
+		goto cleanup;
+
+	if (WEXITSTATUS(wstatus) > 7)
+		ASSERT_OK(WEXITSTATUS(wstatus) - 7, "vpid_test_failure");
+	else
+		ASSERT_OK(WEXITSTATUS(wstatus), "run_vpid_test_err");
+cleanup:
+	free(stack);
+}
+
 static const char * const success_tests[] = {
 	"test_task_acquire_release_argument",
 	"test_task_acquire_release_current",
@@ -83,6 +151,11 @@ static const char * const success_tests[] = {
 	"test_task_kfunc_flavor_relo_not_found",
 };
 
+static const char * const vpid_success_tests[] = {
+	"test_task_from_vpid_current",
+	"test_task_from_vpid_invalid",
+};
+
 void test_task_kfunc(void)
 {
 	int i;
@@ -94,5 +167,12 @@ void test_task_kfunc(void)
 		run_success_test(success_tests[i]);
 	}
 
+	for (i = 0; i < ARRAY_SIZE(vpid_success_tests); i++) {
+		if (!test__start_subtest(vpid_success_tests[i]))
+			continue;
+
+		run_vpid_success_test(vpid_success_tests[i]);
+	}
+
 	RUN_TESTS(task_kfunc_failure);
 }
diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_common.h b/tools/testing/selftests/bpf/progs/task_kfunc_common.h
index 6720c4b5be41..e9c4fea7a4bb 100644
--- a/tools/testing/selftests/bpf/progs/task_kfunc_common.h
+++ b/tools/testing/selftests/bpf/progs/task_kfunc_common.h
@@ -23,6 +23,7 @@ struct {
 struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym;
 void bpf_task_release(struct task_struct *p) __ksym;
 struct task_struct *bpf_task_from_pid(s32 pid) __ksym;
+struct task_struct *bpf_task_from_vpid(s32 vpid) __ksym;
 void bpf_rcu_read_lock(void) __ksym;
 void bpf_rcu_read_unlock(void) __ksym;
 
diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
index ad88a3796ddf..4c07ea193f72 100644
--- a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
+++ b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
@@ -247,6 +247,20 @@ int BPF_PROG(task_kfunc_from_pid_no_null_check, struct task_struct *task, u64 cl
 	return 0;
 }
 
+SEC("tp_btf/task_newtask")
+__failure __msg("Possibly NULL pointer passed to trusted arg0")
+int BPF_PROG(task_kfunc_from_vpid_no_null_check, struct task_struct *task, u64 clone_flags)
+{
+	struct task_struct *acquired;
+
+	acquired = bpf_task_from_vpid(task->pid);
+
+	/* Releasing bpf_task_from_vpid() lookup without a NULL check. */
+	bpf_task_release(acquired);
+
+	return 0;
+}
+
 SEC("lsm/task_free")
 __failure __msg("R1 must be a rcu pointer")
 int BPF_PROG(task_kfunc_from_lsm_task_free, struct task_struct *task)
diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_success.c b/tools/testing/selftests/bpf/progs/task_kfunc_success.c
index a55149015063..5fb4fc19d26a 100644
--- a/tools/testing/selftests/bpf/progs/task_kfunc_success.c
+++ b/tools/testing/selftests/bpf/progs/task_kfunc_success.c
@@ -366,3 +366,54 @@ int BPF_PROG(task_kfunc_acquire_trusted_walked, struct task_struct *task, u64 cl
 
 	return 0;
 }
+
+SEC("syscall")
+int test_task_from_vpid_current(const void *ctx)
+{
+	struct task_struct *current, *v_task;
+
+	v_task = bpf_task_from_vpid(1);
+	if (!v_task) {
+		err = 1;
+		return 0;
+	}
+
+	current = bpf_get_current_task_btf();
+
+	/* The current process should be the init process (pid 1) in the new pid namespace. */
+	if (current != v_task)
+		err = 2;
+
+	bpf_task_release(v_task);
+	return 0;
+}
+
+SEC("syscall")
+int test_task_from_vpid_invalid(const void *ctx)
+{
+	struct task_struct *v_task;
+
+	v_task = bpf_task_from_vpid(-1);
+	if (v_task) {
+		err = 1;
+		goto err;
+	}
+
+	/* There should be only one process (current process) in the new pid namespace. */
+	v_task = bpf_task_from_vpid(2);
+	if (v_task) {
+		err = 2;
+		goto err;
+	}
+
+	v_task = bpf_task_from_vpid(9999);
+	if (v_task) {
+		err = 3;
+		goto err;
+	}
+
+	return 0;
+err:
+	bpf_task_release(v_task);
+	return 0;
+}
-- 
2.39.5

Re: [PATCH bpf-next 1/2] bpf: Add bpf_task_from_vpid() kfunc

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Mon, 14 Oct 2024 10:21:08 +0100 you wrote:
> bpf_task_from_pid() that currently exists looks up the
> struct task_struct corresponding to the pid in the root pid
> namespace (init_pid_ns).
> 
> This patch adds bpf_task_from_vpid() which looks up the
> struct task_struct corresponding to vpid in the pid namespace
> of the current process.
> 
> [...]

Here is the summary with links:
  - [bpf-next,1/2] bpf: Add bpf_task_from_vpid() kfunc
    https://git.kernel.org/bpf/bpf-next/c/6dce087f24e5
  - [bpf-next,2/2] selftests/bpf: Add tests for bpf_task_from_vpid() kfunc
    https://git.kernel.org/bpf/bpf-next/c/108e7b4db83b

You are awesome, thank you!
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