test_d_path_check_rdonly_mem.c

 1// SPDX-License-Identifier: GPL-2.0
 2/* Copyright (c) 2022 Google */
 3
 4#include "vmlinux.h"
 5#include <bpf/bpf_helpers.h>
 6#include <bpf/bpf_tracing.h>
 7
 8extern const int bpf_prog_active __ksym;
 9
10SEC("fentry/security_inode_getattr")
11int BPF_PROG(d_path_check_rdonly_mem, struct path *path, struct kstat *stat,
12	     __u32 request_mask, unsigned int query_flags)
13{
14	void *active;
15	__u32 cpu;
16
17	cpu = bpf_get_smp_processor_id();
18	active = (void *)bpf_per_cpu_ptr(&bpf_prog_active, cpu);
19	if (active) {
20		/* FAIL here! 'active' points to readonly memory. bpf helpers
21		 * that update its arguments can not write into it.
22		 */
23		bpf_d_path(path, active, sizeof(int));
24	}
25	return 0;
26}
27
28char _license[] SEC("license") = "GPL";