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@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 155 insertions, 2 deletions

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 9fbb02638198..333a48655ee0 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -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
 
diff --git a/tools/testing/selftests/bpf/dev_cgroup.c b/tools/testing/selftests/bpf/dev_cgroup.c
new file mode 100644
index 000000000000..ce41a3475f27
--- /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 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;
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;
+}