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// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
#include <vmlinux.h>
#include <bpf/bpf_tracing.h>
#include <bpf/bpf_helpers.h>
#include "bpf_misc.h"
#include "task_kfunc_common.h"
char _license[] SEC("license") = "GPL";
/* Prototype for all of the program trace events below:
*
* TRACE_EVENT(task_newtask,
* TP_PROTO(struct task_struct *p, u64 clone_flags)
*/
static struct __tasks_kfunc_map_value *insert_lookup_task(struct task_struct *task)
{
int status;
status = tasks_kfunc_map_insert(task);
if (status)
return NULL;
return tasks_kfunc_map_value_lookup(task);
}
SEC("tp_btf/task_newtask")
__failure __msg("Possibly NULL pointer passed to trusted arg0")
int BPF_PROG(task_kfunc_acquire_untrusted, struct task_struct *task, u64 clone_flags)
{
struct task_struct *acquired;
struct __tasks_kfunc_map_value *v;
v = insert_lookup_task(task);
if (!v)
return 0;
/* Can't invoke bpf_task_acquire() on an untrusted pointer. */
acquired = bpf_task_acquire(v->task);
if (!acquired)
return 0;
bpf_task_release(acquired);
return 0;
}
SEC("tp_btf/task_newtask")
__failure __msg("arg#0 pointer type STRUCT task_struct must point")
int BPF_PROG(task_kfunc_acquire_fp, struct task_struct *task, u64 clone_flags)
{
struct task_struct *acquired, *stack_task = (struct task_struct *)&clone_flags;
/* Can't invoke bpf_task_acquire() on a random frame pointer. */
acquired = bpf_task_acquire((struct task_struct *)&stack_task);
if (!acquired)
return 0;
bpf_task_release(acquired);
return 0;
}
SEC("kretprobe/free_task")
__failure __msg("calling kernel function bpf_task_acquire is not allowed")
int BPF_PROG(task_kfunc_acquire_unsafe_kretprobe, struct task_struct *task, u64 clone_flags)
{
struct task_struct *acquired;
/* Can't call bpf_task_acquire() or bpf_task_release() in an untrusted prog. */
acquired = bpf_task_acquire(task);
if (!acquired)
return 0;
bpf_task_release(acquired);
return 0;
}
SEC("kretprobe/free_task")
__failure __msg("calling kernel function bpf_task_acquire is not allowed")
int BPF_PROG(task_kfunc_acquire_unsafe_kretprobe_rcu, struct task_struct *task, u64 clone_flags)
{
struct task_struct *acquired;
bpf_rcu_read_lock();
if (!task) {
bpf_rcu_read_unlock();
return 0;
}
/* Can't call bpf_task_acquire() or bpf_task_release() in an untrusted prog. */
acquired = bpf_task_acquire(task);
if (acquired)
bpf_task_release(acquired);
bpf_rcu_read_unlock();
return 0;
}
SEC("tp_btf/task_newtask")
__failure __msg("Possibly NULL pointer passed to trusted arg0")
int BPF_PROG(task_kfunc_acquire_null, struct task_struct *task, u64 clone_flags)
{
struct task_struct *acquired;
/* Can't invoke bpf_task_acquire() on a NULL pointer. */
acquired = bpf_task_acquire(NULL);
if (!acquired)
return 0;
bpf_task_release(acquired);
return 0;
}
SEC("tp_btf/task_newtask")
__failure __msg("Unreleased reference")
int BPF_PROG(task_kfunc_acquire_unreleased, struct task_struct *task, u64 clone_flags)
{
struct task_struct *acquired;
acquired = bpf_task_acquire(task);
/* Acquired task is never released. */
__sink(acquired);
return 0;
}
SEC("tp_btf/task_newtask")
__failure __msg("Unreleased reference")
int BPF_PROG(task_kfunc_xchg_unreleased, struct task_struct *task, u64 clone_flags)
{
struct task_struct *kptr;
struct __tasks_kfunc_map_value *v;
v = insert_lookup_task(task);
if (!v)
return 0;
kptr = bpf_kptr_xchg(&v->task, NULL);
if (!kptr)
return 0;
/* Kptr retrieved from map is never released. */
return 0;
}
SEC("tp_btf/task_newtask")
__failure __msg("Possibly NULL pointer passed to trusted arg0")
int BPF_PROG(task_kfunc_acquire_release_no_null_check, struct task_struct *task, u64 clone_flags)
{
struct task_struct *acquired;
acquired = bpf_task_acquire(task);
/* Can't invoke bpf_task_release() on an acquired task without a NULL check. */
bpf_task_release(acquired);
return 0;
}
SEC("tp_btf/task_newtask")
__failure __msg("Possibly NULL pointer passed to trusted arg0")
int BPF_PROG(task_kfunc_release_untrusted, struct task_struct *task, u64 clone_flags)
{
struct __tasks_kfunc_map_value *v;
v = insert_lookup_task(task);
if (!v)
return 0;
/* Can't invoke bpf_task_release() on an untrusted pointer. */
bpf_task_release(v->task);
return 0;
}
SEC("tp_btf/task_newtask")
__failure __msg("arg#0 pointer type STRUCT task_struct must point")
int BPF_PROG(task_kfunc_release_fp, struct task_struct *task, u64 clone_flags)
{
struct task_struct *acquired = (struct task_struct *)&clone_flags;
/* Cannot release random frame pointer. */
bpf_task_release(acquired);
return 0;
}
SEC("tp_btf/task_newtask")
__failure __msg("Possibly NULL pointer passed to trusted arg0")
int BPF_PROG(task_kfunc_release_null, struct task_struct *task, u64 clone_flags)
{
struct __tasks_kfunc_map_value local, *v;
long status;
struct task_struct *acquired, *old;
s32 pid;
status = bpf_probe_read_kernel(&pid, sizeof(pid), &task->pid);
if (status)
return 0;
local.task = NULL;
status = bpf_map_update_elem(&__tasks_kfunc_map, &pid, &local, BPF_NOEXIST);
if (status)
return status;
v = bpf_map_lookup_elem(&__tasks_kfunc_map, &pid);
if (!v)
return -ENOENT;
acquired = bpf_task_acquire(task);
if (!acquired)
return -EEXIST;
old = bpf_kptr_xchg(&v->task, acquired);
/* old cannot be passed to bpf_task_release() without a NULL check. */
bpf_task_release(old);
return 0;
}
SEC("tp_btf/task_newtask")
__failure __msg("release kernel function bpf_task_release expects")
int BPF_PROG(task_kfunc_release_unacquired, struct task_struct *task, u64 clone_flags)
{
/* Cannot release trusted task pointer which was not acquired. */
bpf_task_release(task);
return 0;
}
SEC("tp_btf/task_newtask")
__failure __msg("Possibly NULL pointer passed to trusted arg0")
int BPF_PROG(task_kfunc_from_pid_no_null_check, struct task_struct *task, u64 clone_flags)
{
struct task_struct *acquired;
acquired = bpf_task_from_pid(task->pid);
/* Releasing bpf_task_from_pid() lookup without a NULL check. */
bpf_task_release(acquired);
return 0;
}
SEC("lsm/task_free")
__failure __msg("reg type unsupported for arg#0 function")
int BPF_PROG(task_kfunc_from_lsm_task_free, struct task_struct *task)
{
struct task_struct *acquired;
/* the argument of lsm task_free hook is untrusted. */
acquired = bpf_task_acquire(task);
if (!acquired)
return 0;
bpf_task_release(acquired);
return 0;
}
SEC("tp_btf/task_newtask")
__failure __msg("access beyond the end of member comm")
int BPF_PROG(task_access_comm1, struct task_struct *task, u64 clone_flags)
{
bpf_strncmp(task->comm, 17, "foo");
return 0;
}
SEC("tp_btf/task_newtask")
__failure __msg("access beyond the end of member comm")
int BPF_PROG(task_access_comm2, struct task_struct *task, u64 clone_flags)
{
bpf_strncmp(task->comm + 1, 16, "foo");
return 0;
}
SEC("tp_btf/task_newtask")
__failure __msg("write into memory")
int BPF_PROG(task_access_comm3, struct task_struct *task, u64 clone_flags)
{
bpf_probe_read_kernel(task->comm, 16, task->comm);
return 0;
}
SEC("fentry/__set_task_comm")
__failure __msg("R1 type=ptr_ expected")
int BPF_PROG(task_access_comm4, struct task_struct *task, const char *buf, bool exec)
{
/*
* task->comm is a legacy ptr_to_btf_id. The verifier cannot guarantee
* its safety. Hence it cannot be accessed with normal load insns.
*/
bpf_strncmp(task->comm, 16, "foo");
return 0;
}
SEC("tp_btf/task_newtask")
__failure __msg("R1 must be referenced or trusted")
int BPF_PROG(task_kfunc_release_in_map, struct task_struct *task, u64 clone_flags)
{
struct task_struct *local;
struct __tasks_kfunc_map_value *v;
if (tasks_kfunc_map_insert(task))
return 0;
v = tasks_kfunc_map_value_lookup(task);
if (!v)
return 0;
bpf_rcu_read_lock();
local = v->task;
if (!local) {
bpf_rcu_read_unlock();
return 0;
}
/* Can't release a kptr that's still stored in a map. */
bpf_task_release(local);
bpf_rcu_read_unlock();
return 0;
}
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