Commit 44bab87d authored by Hao Luo's avatar Hao Luo Committed by Andrii Nakryiko
Browse files

bpf/selftests: Test bpf_d_path on rdonly_mem. 



The second parameter of bpf_d_path() can only accept writable
memories. Rdonly_mem obtained from bpf_per_cpu_ptr() can not
be passed into bpf_d_path for modification. This patch adds
a selftest to verify this behavior.

Signed-off-by: default avatarHao Luo <haoluo@google.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20220106205525.2116218-1-haoluo@google.com
parent e59618f0

tools/testing/selftests/bpf/prog_tests/d_path.c

+21 −1
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ 
#define MAX_FILES		7



#include "test_d_path.skel.h"

#include "test_d_path_check_rdonly_mem.skel.h"



static int duration;
@@ -99,7 +100,7 @@ static int trigger_fstat_events(pid_t pid) 
	return ret;

}



void test_d_path(void)

static void test_d_path_basic(void)

{

	struct test_d_path__bss *bss;

	struct test_d_path *skel;
@@ -155,3 +156,22 @@ void test_d_path(void) 
cleanup:

	test_d_path__destroy(skel);

}



static void test_d_path_check_rdonly_mem(void)

{

	struct test_d_path_check_rdonly_mem *skel;



	skel = test_d_path_check_rdonly_mem__open_and_load();

	ASSERT_ERR_PTR(skel, "unexpected_load_overwriting_rdonly_mem");



	test_d_path_check_rdonly_mem__destroy(skel);

}



void test_d_path(void)

{

	if (test__start_subtest("basic"))

		test_d_path_basic();



	if (test__start_subtest("check_rdonly_mem"))

		test_d_path_check_rdonly_mem();

}

tools/testing/selftests/bpf/progs/test_d_path_check_rdonly_mem.c

0 → 100644
+28 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/* Copyright (c) 2022 Google */



#include "vmlinux.h"

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>



extern const int bpf_prog_active __ksym;



SEC("fentry/security_inode_getattr")

int BPF_PROG(d_path_check_rdonly_mem, struct path *path, struct kstat *stat,

	     __u32 request_mask, unsigned int query_flags)

{

	void *active;

	__u32 cpu;



	cpu = bpf_get_smp_processor_id();

	active = (void *)bpf_per_cpu_ptr(&bpf_prog_active, cpu);

	if (active) {

		/* FAIL here! 'active' points to readonly memory. bpf helpers

		 * that update its arguments can not write into it.

		 */

		bpf_d_path(path, active, sizeof(int));

	}

	return 0;

}



char _license[] SEC("license") = "GPL";