1*44bab87dSHao Luo // SPDX-License-Identifier: GPL-2.0
2*44bab87dSHao Luo /* Copyright (c) 2022 Google */
3*44bab87dSHao Luo
4*44bab87dSHao Luo #include "vmlinux.h"
5*44bab87dSHao Luo #include <bpf/bpf_helpers.h>
6*44bab87dSHao Luo #include <bpf/bpf_tracing.h>
7*44bab87dSHao Luo
8*44bab87dSHao Luo extern const int bpf_prog_active __ksym;
9*44bab87dSHao Luo
10*44bab87dSHao Luo SEC("fentry/security_inode_getattr")
BPF_PROG(d_path_check_rdonly_mem,struct path * path,struct kstat * stat,__u32 request_mask,unsigned int query_flags)11*44bab87dSHao Luo int BPF_PROG(d_path_check_rdonly_mem, struct path *path, struct kstat *stat,
12*44bab87dSHao Luo __u32 request_mask, unsigned int query_flags)
13*44bab87dSHao Luo {
14*44bab87dSHao Luo void *active;
15*44bab87dSHao Luo __u32 cpu;
16*44bab87dSHao Luo
17*44bab87dSHao Luo cpu = bpf_get_smp_processor_id();
18*44bab87dSHao Luo active = (void *)bpf_per_cpu_ptr(&bpf_prog_active, cpu);
19*44bab87dSHao Luo if (active) {
20*44bab87dSHao Luo /* FAIL here! 'active' points to readonly memory. bpf helpers
21*44bab87dSHao Luo * that update its arguments can not write into it.
22*44bab87dSHao Luo */
23*44bab87dSHao Luo bpf_d_path(path, active, sizeof(int));
24*44bab87dSHao Luo }
25*44bab87dSHao Luo return 0;
26*44bab87dSHao Luo }
27*44bab87dSHao Luo
28*44bab87dSHao Luo char _license[] SEC("license") = "GPL";
29