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Subject[PATCH v3 bpf-next 10/21] selftests/bpf: Test BPF_CGROUP_SYSCTL
Date
Add unit test for BPF_PROG_TYPE_CGROUP_SYSCTL program type.

Test that program can allow/deny access.
Test both valid and invalid accesses to ctx->write.

Example of output:
# ./test_sysctl
Test case: sysctl wrong attach_type .. [PASS]
Test case: sysctl:read allow all .. [PASS]
Test case: sysctl:read deny all .. [PASS]
Test case: ctx:write sysctl:read read ok .. [PASS]
Test case: ctx:write sysctl:write read ok .. [PASS]
Test case: ctx:write sysctl:read write reject .. [PASS]
Summary: 6 PASSED, 0 FAILED

Signed-off-by: Andrey Ignatov <rdna@fb.com>
---
tools/testing/selftests/bpf/Makefile | 3 +-
tools/testing/selftests/bpf/test_sysctl.c | 291 ++++++++++++++++++++++
2 files changed, 293 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/bpf/test_sysctl.c

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 078283d073b0..f9d83ba7843e 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -23,7 +23,7 @@ TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test
test_align test_verifier_log test_dev_cgroup test_tcpbpf_user \
test_sock test_btf test_sockmap test_lirc_mode2_user get_cgroup_id_user \
test_socket_cookie test_cgroup_storage test_select_reuseport test_section_names \
- test_netcnt test_tcpnotify_user test_sock_fields
+ test_netcnt test_tcpnotify_user test_sock_fields test_sysctl

BPF_OBJ_FILES = $(patsubst %.c,%.o, $(notdir $(wildcard progs/*.c)))
TEST_GEN_FILES = $(BPF_OBJ_FILES)
@@ -93,6 +93,7 @@ $(OUTPUT)/get_cgroup_id_user: cgroup_helpers.c
$(OUTPUT)/test_cgroup_storage: cgroup_helpers.c
$(OUTPUT)/test_netcnt: cgroup_helpers.c
$(OUTPUT)/test_sock_fields: cgroup_helpers.c
+$(OUTPUT)/test_sysctl: cgroup_helpers.c

.PHONY: force

diff --git a/tools/testing/selftests/bpf/test_sysctl.c b/tools/testing/selftests/bpf/test_sysctl.c
new file mode 100644
index 000000000000..6d0ab09789ad
--- /dev/null
+++ b/tools/testing/selftests/bpf/test_sysctl.c
@@ -0,0 +1,291 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <fcntl.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <linux/filter.h>
+
+#include <bpf/bpf.h>
+
+#include "bpf_rlimit.h"
+#include "bpf_util.h"
+#include "cgroup_helpers.h"
+
+#define CG_PATH "/foo"
+#define MAX_INSNS 512
+
+char bpf_log_buf[BPF_LOG_BUF_SIZE];
+
+struct sysctl_test {
+ const char *descr;
+ struct bpf_insn insns[MAX_INSNS];
+ enum bpf_attach_type attach_type;
+ const char *sysctl;
+ int open_flags;
+ const char *newval;
+ enum {
+ LOAD_REJECT,
+ ATTACH_REJECT,
+ OP_EPERM,
+ SUCCESS,
+ } result;
+};
+
+static struct sysctl_test tests[] = {
+ {
+ .descr = "sysctl wrong attach_type",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_EXIT_INSN(),
+ },
+ .attach_type = 0,
+ .sysctl = "kernel/ostype",
+ .open_flags = O_RDONLY,
+ .result = ATTACH_REJECT,
+ },
+ {
+ .descr = "sysctl:read allow all",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_EXIT_INSN(),
+ },
+ .attach_type = BPF_CGROUP_SYSCTL,
+ .sysctl = "kernel/ostype",
+ .open_flags = O_RDONLY,
+ .result = SUCCESS,
+ },
+ {
+ .descr = "sysctl:read deny all",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .attach_type = BPF_CGROUP_SYSCTL,
+ .sysctl = "kernel/ostype",
+ .open_flags = O_RDONLY,
+ .result = OP_EPERM,
+ },
+ {
+ .descr = "ctx:write sysctl:read read ok",
+ .insns = {
+ /* If (write) */
+ BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_1,
+ offsetof(struct bpf_sysctl, write)),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_7, 1, 2),
+
+ /* return DENY; */
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_JMP_A(1),
+
+ /* else return ALLOW; */
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_EXIT_INSN(),
+ },
+ .attach_type = BPF_CGROUP_SYSCTL,
+ .sysctl = "kernel/ostype",
+ .open_flags = O_RDONLY,
+ .result = SUCCESS,
+ },
+ {
+ .descr = "ctx:write sysctl:write read ok",
+ .insns = {
+ /* If (write) */
+ BPF_LDX_MEM(BPF_B, BPF_REG_7, BPF_REG_1,
+ offsetof(struct bpf_sysctl, write)),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_7, 1, 2),
+
+ /* return DENY; */
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_JMP_A(1),
+
+ /* else return ALLOW; */
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_EXIT_INSN(),
+ },
+ .attach_type = BPF_CGROUP_SYSCTL,
+ .sysctl = "kernel/domainname",
+ .open_flags = O_WRONLY,
+ .newval = "(none)", /* same as default, should fail anyway */
+ .result = OP_EPERM,
+ },
+ {
+ .descr = "ctx:write sysctl:read write reject",
+ .insns = {
+ /* write = X */
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_0,
+ offsetof(struct bpf_sysctl, write)),
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_EXIT_INSN(),
+ },
+ .attach_type = BPF_CGROUP_SYSCTL,
+ .sysctl = "kernel/ostype",
+ .open_flags = O_RDONLY,
+ .result = LOAD_REJECT,
+ },
+};
+
+static size_t probe_prog_length(const struct bpf_insn *fp)
+{
+ size_t len;
+
+ for (len = MAX_INSNS - 1; len > 0; --len)
+ if (fp[len].code != 0 || fp[len].imm != 0)
+ break;
+ return len + 1;
+}
+
+static int load_sysctl_prog(struct sysctl_test *test, const char *sysctl_path)
+{
+ struct bpf_insn *prog = test->insns;
+ struct bpf_load_program_attr attr;
+ int ret;
+
+ memset(&attr, 0, sizeof(struct bpf_load_program_attr));
+ attr.prog_type = BPF_PROG_TYPE_CGROUP_SYSCTL;
+ attr.insns = prog;
+ attr.insns_cnt = probe_prog_length(attr.insns);
+ attr.license = "GPL";
+
+ ret = bpf_load_program_xattr(&attr, bpf_log_buf, BPF_LOG_BUF_SIZE);
+ if (ret < 0 && test->result != LOAD_REJECT) {
+ log_err(">>> Loading program error.\n"
+ ">>> Verifier output:\n%s\n-------\n", bpf_log_buf);
+ }
+
+ return ret;
+}
+
+static int access_sysctl(const char *sysctl_path,
+ const struct sysctl_test *test)
+{
+ int err = 0;
+ int fd;
+
+ fd = open(sysctl_path, test->open_flags | O_CLOEXEC);
+ if (fd < 0)
+ return fd;
+
+ if (test->open_flags == O_RDONLY) {
+ char buf[128];
+
+ if (read(fd, buf, sizeof(buf)) == -1)
+ goto err;
+ } else if (test->open_flags == O_WRONLY) {
+ if (!test->newval) {
+ log_err("New value for sysctl is not set");
+ goto err;
+ }
+ if (write(fd, test->newval, strlen(test->newval)) == -1)
+ goto err;
+ } else {
+ log_err("Unexpected sysctl access: neither read nor write");
+ goto err;
+ }
+
+ goto out;
+err:
+ err = -1;
+out:
+ close(fd);
+ return err;
+}
+
+static int run_test_case(int cgfd, struct sysctl_test *test)
+{
+ enum bpf_attach_type atype = test->attach_type;
+ char sysctl_path[128];
+ int progfd = -1;
+ int err = 0;
+
+ printf("Test case: %s .. ", test->descr);
+
+ snprintf(sysctl_path, sizeof(sysctl_path), "/proc/sys/%s",
+ test->sysctl);
+
+ progfd = load_sysctl_prog(test, sysctl_path);
+ if (progfd < 0) {
+ if (test->result == LOAD_REJECT)
+ goto out;
+ else
+ goto err;
+ }
+
+ if (bpf_prog_attach(progfd, cgfd, atype, BPF_F_ALLOW_OVERRIDE) == -1) {
+ if (test->result == ATTACH_REJECT)
+ goto out;
+ else
+ goto err;
+ }
+
+ if (access_sysctl(sysctl_path, test) == -1) {
+ if (test->result == OP_EPERM && errno == EPERM)
+ goto out;
+ else
+ goto err;
+ }
+
+ if (test->result != SUCCESS) {
+ log_err("Unexpected failure");
+ goto err;
+ }
+
+ goto out;
+err:
+ err = -1;
+out:
+ /* Detaching w/o checking return code: best effort attempt. */
+ if (progfd != -1)
+ bpf_prog_detach(cgfd, atype);
+ close(progfd);
+ printf("[%s]\n", err ? "FAIL" : "PASS");
+ return err;
+}
+
+static int run_tests(int cgfd)
+{
+ int passes = 0;
+ int fails = 0;
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(tests); ++i) {
+ if (run_test_case(cgfd, &tests[i]))
+ ++fails;
+ else
+ ++passes;
+ }
+ printf("Summary: %d PASSED, %d FAILED\n", passes, fails);
+ return fails ? -1 : 0;
+}
+
+int main(int argc, char **argv)
+{
+ int cgfd = -1;
+ int err = 0;
+
+ if (setup_cgroup_environment())
+ goto err;
+
+ cgfd = create_and_get_cgroup(CG_PATH);
+ if (cgfd < 0)
+ goto err;
+
+ if (join_cgroup(CG_PATH))
+ goto err;
+
+ if (run_tests(cgfd))
+ goto err;
+
+ goto out;
+err:
+ err = -1;
+out:
+ close(cgfd);
+ cleanup_cgroup_environment();
+ return err;
+}
--
2.17.1
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