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Message-ID: <20171101152037.3288-5-guro@fb.com>
Date: Wed, 1 Nov 2017 11:20:37 -0400
From: Roman Gushchin <guro@...com>
To: <netdev@...r.kernel.org>
CC: Tejun Heo <tj@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
<linux-kernel@...r.kernel.org>, Roman Gushchin <guro@...com>
Subject: [PATCH net-next 4/4] 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: Roman Gushchin <guro@...com>
Acked-by: Alexei Starovoitov <ast@...nel.org>
Acked-by: Tejun Heo <tj@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>
---
tools/testing/selftests/bpf/Makefile | 4 +-
tools/testing/selftests/bpf/dev_cgroup.c | 60 +++++++++++++++++
tools/testing/selftests/bpf/test_dev_cgroup.c | 93 +++++++++++++++++++++++++++
3 files changed, 155 insertions(+), 2 deletions(-)
create mode 100644 tools/testing/selftests/bpf/dev_cgroup.c
create mode 100644 tools/testing/selftests/bpf/test_dev_cgroup.c
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 36c34f0218a3..64ba3684a4f4 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -12,11 +12,11 @@ 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
diff --git a/tools/testing/selftests/bpf/dev_cgroup.c b/tools/testing/selftests/bpf/dev_cgroup.c
new file mode 100644
index 000000000000..f15d5befa099
--- /dev/null
+++ b/tools/testing/selftests/bpf/dev_cgroup.c
@@ -0,0 +1,60 @@
+/* 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 DEV_BPF_DEV_BLOCK:
+ fmt[0] = 'b';
+ break;
+ case DEV_BPF_DEV_CHAR:
+ fmt[0] = 'c';
+ break;
+ default:
+ fmt[0] = '?';
+ break;
+ }
+
+ if (access & DEV_BPF_ACC_READ)
+ fmt[8] = 'r';
+
+ if (access & DEV_BPF_ACC_WRITE)
+ fmt[9] = 'w';
+
+ if (access & DEV_BPF_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 != DEV_BPF_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;
diff --git a/tools/testing/selftests/bpf/test_dev_cgroup.c b/tools/testing/selftests/bpf/test_dev_cgroup.c
new file mode 100644
index 000000000000..02c85d6c89b0
--- /dev/null
+++ b/tools/testing/selftests/bpf/test_dev_cgroup.c
@@ -0,0 +1,93 @@
+/* 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;
+}
--
2.13.6
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