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Commit 37f1ba09 authored by Roman Gushchin's avatar Roman Gushchin Committed by David S. Miller
Browse files

selftests/bpf: add a test for device cgroup controller 



Add a test for device cgroup controller.

The test loads a simple bpf program which logs all
device access attempts using trace_printk() and forbids
all operations except operations with /dev/zero and
/dev/urandom.

Then the test creates and joins a test cgroup, and attaches
the bpf program to it.

Then it tries to perform some simple device operations
and checks the result:

  create /dev/null (should fail)
  create /dev/zero (should pass)
  copy data from /dev/urandom to /dev/zero (should pass)
  copy data from /dev/urandom to /dev/full (should fail)
  copy data from /dev/random to /dev/zero (should fail)

Signed-off-by: default avatarRoman Gushchin <guro@fb.com>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9d1f1594

tools/testing/selftests/bpf/Makefile

+2 −2
Original line number Diff line number Diff line
@@ -13,11 +13,11 @@ CFLAGS += -Wall -O2 -I$(APIDIR) -I$(LIBDIR) -I$(GENDIR) $(GENFLAGS) -I../../../i 
LDLIBS += -lcap -lelf



TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test_progs \

	test_align test_verifier_log

	test_align test_verifier_log test_dev_cgroup



TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test_obj_id.o \

	test_pkt_md_access.o test_xdp_redirect.o test_xdp_meta.o sockmap_parse_prog.o     \

	sockmap_verdict_prog.o

	sockmap_verdict_prog.o dev_cgroup.o



TEST_PROGS := test_kmod.sh test_xdp_redirect.sh test_xdp_meta.sh

tools/testing/selftests/bpf/dev_cgroup.c

0 → 100644
+60 −0
Original line number Diff line number Diff line 
/* Copyright (c) 2017 Facebook

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of version 2 of the GNU General Public

 * License as published by the Free Software Foundation.

 */



#include <linux/bpf.h>

#include <linux/version.h>

#include "bpf_helpers.h"



SEC("cgroup/dev")

int bpf_prog1(struct bpf_cgroup_dev_ctx *ctx)

{

	short type = ctx->access_type & 0xFFFF;

#ifdef DEBUG

	short access = ctx->access_type >> 16;

	char fmt[] = "  %d:%d    \n";



	switch (type) {

	case BPF_DEVCG_DEV_BLOCK:

		fmt[0] = 'b';

		break;

	case BPF_DEVCG_DEV_CHAR:

		fmt[0] = 'c';

		break;

	default:

		fmt[0] = '?';

		break;

	}



	if (access & BPF_DEVCG_ACC_READ)

		fmt[8] = 'r';



	if (access & BPF_DEVCG_ACC_WRITE)

		fmt[9] = 'w';



	if (access & BPF_DEVCG_ACC_MKNOD)

		fmt[10] = 'm';



	bpf_trace_printk(fmt, sizeof(fmt), ctx->major, ctx->minor);

#endif



	/* Allow access to /dev/zero and /dev/random.

	 * Forbid everything else.

	 */

	if (ctx->major != 1 || type != BPF_DEVCG_DEV_CHAR)

		return 0;



	switch (ctx->minor) {

	case 5: /* 1:5 /dev/zero */

	case 9: /* 1:9 /dev/urandom */

		return 1;

	}



	return 0;

}



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

__u32 _version SEC("version") = LINUX_VERSION_CODE;

tools/testing/selftests/bpf/test_dev_cgroup.c

0 → 100644
+93 −0
Original line number Diff line number Diff line 
/* Copyright (c) 2017 Facebook

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of version 2 of the GNU General Public

 * License as published by the Free Software Foundation.

 */



#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <errno.h>

#include <assert.h>



#include <linux/bpf.h>

#include <bpf/bpf.h>

#include <bpf/libbpf.h>



#include "cgroup_helpers.h"



#define DEV_CGROUP_PROG "./dev_cgroup.o"



#define TEST_CGROUP "test-bpf-based-device-cgroup/"



int main(int argc, char **argv)

{

	struct bpf_object *obj;

	int error = EXIT_FAILURE;

	int prog_fd, cgroup_fd;

	__u32 prog_cnt;



	if (bpf_prog_load(DEV_CGROUP_PROG, BPF_PROG_TYPE_CGROUP_DEVICE,

			  &obj, &prog_fd)) {

		printf("Failed to load DEV_CGROUP program\n");

		goto err;

	}



	if (setup_cgroup_environment()) {

		printf("Failed to load DEV_CGROUP program\n");

		goto err;

	}



	/* Create a cgroup, get fd, and join it */

	cgroup_fd = create_and_get_cgroup(TEST_CGROUP);

	if (!cgroup_fd) {

		printf("Failed to create test cgroup\n");

		goto err;

	}



	if (join_cgroup(TEST_CGROUP)) {

		printf("Failed to join cgroup\n");

		goto err;

	}



	/* Attach bpf program */

	if (bpf_prog_attach(prog_fd, cgroup_fd, BPF_CGROUP_DEVICE, 0)) {

		printf("Failed to attach DEV_CGROUP program");

		goto err;

	}



	if (bpf_prog_query(cgroup_fd, BPF_CGROUP_DEVICE, 0, NULL, NULL,

			   &prog_cnt)) {

		printf("Failed to query attached programs");

		goto err;

	}



	/* All operations with /dev/zero and and /dev/urandom are allowed,

	 * everything else is forbidden.

	 */

	assert(system("rm -f /tmp/test_dev_cgroup_null") == 0);

	assert(system("mknod /tmp/test_dev_cgroup_null c 1 3"));

	assert(system("rm -f /tmp/test_dev_cgroup_null") == 0);



	/* /dev/zero is whitelisted */

	assert(system("rm -f /tmp/test_dev_cgroup_zero") == 0);

	assert(system("mknod /tmp/test_dev_cgroup_zero c 1 5") == 0);

	assert(system("rm -f /tmp/test_dev_cgroup_zero") == 0);



	assert(system("dd if=/dev/urandom of=/dev/zero count=64") == 0);



	/* src is allowed, target is forbidden */

	assert(system("dd if=/dev/urandom of=/dev/full count=64"));



	/* src is forbidden, target is allowed */

	assert(system("dd if=/dev/random of=/dev/zero count=64"));



	error = 0;

	printf("test_dev_cgroup:PASS\n");



err:

	cleanup_cgroup_environment();



	return error;

}