lkml.org 
[lkml]   [2019]   [Dec]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH bpf-next v1 12/13] bpf: lsm: Add selftests for BPF_PROG_TYPE_LSM
On Fri, Dec 20, 2019 at 7:42 AM KP Singh <kpsingh@chromium.org> wrote:
>
> From: KP Singh <kpsingh@google.com>
>
> * Load a BPF program that audits mprotect calls
> * Attach the program to the "file_mprotect" LSM hook
> * Verify if the program is actually loading by reading
> securityfs
> * Initialize the perf events buffer and poll for audit events
> * Do an mprotect on some memory allocated on the heap
> * Verify if the audit event was received
>
> Signed-off-by: KP Singh <kpsingh@google.com>
> ---
> MAINTAINERS | 2 +
> .../bpf/prog_tests/lsm_mprotect_audit.c | 129 ++++++++++++++++++
> .../selftests/bpf/progs/lsm_mprotect_audit.c | 58 ++++++++
> 3 files changed, 189 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/lsm_mprotect_audit.c
> create mode 100644 tools/testing/selftests/bpf/progs/lsm_mprotect_audit.c
>

[...]

> +/*
> + * Define some of the structs used in the BPF program.
> + * Only the field names and their sizes need to be the
> + * same as the kernel type, the order is irrelevant.
> + */
> +struct mm_struct {
> + unsigned long start_brk, brk, start_stack;
> +};
> +
> +struct vm_area_struct {
> + unsigned long start_brk, brk, start_stack;
> + unsigned long vm_start, vm_end;
> + struct mm_struct *vm_mm;
> + unsigned long vm_flags;
> +};
> +
> +BPF_TRACE_3("lsm/file_mprotect", mprotect_audit,
> + struct vm_area_struct *, vma,
> + unsigned long, reqprot, unsigned long, prot)
> +{
> + struct mprotect_audit_log audit_log = {};
> + int is_heap = 0;
> +
> + __builtin_preserve_access_index(({

you don't need __builtin_preserve_access_index, if you mark
vm_area_struct and mm_struct with
__attribute__((preserve_access_index)

> + is_heap = (vma->vm_start >= vma->vm_mm->start_brk &&
> + vma->vm_end <= vma->vm_mm->brk);
> + }));
> +
> + audit_log.magic = MPROTECT_AUDIT_MAGIC;
> + audit_log.is_heap = is_heap;
> + bpf_lsm_event_output(&perf_buf_map, BPF_F_CURRENT_CPU, &audit_log,
> + sizeof(audit_log));

You test would be much simpler if you use global variables to pass
data back to userspace, instead of using perf buffer.

Also please see fentry_fexit.c test for example of using BPF skeleton
to shorten and simpify userspace part of test.

> + return 0;
> +}
> --
> 2.20.1
>

\
 
 \ /
  Last update: 2019-12-24 07:50    [W:0.245 / U:0.136 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site