On Wed, Sep 7, 2022 at 8:09 PM Alexei Starovoitov alexei.starovoitov@gmail.com wrote:
On Wed, Sep 7, 2022 at 10:46 AM Kumar Kartikeya Dwivedi memxor@gmail.com wrote:
On Tue, 6 Sept 2022 at 17:13, Benjamin Tissoires benjamin.tissoires@redhat.com wrote:
We need to also export the kfunc set to the syscall program type, and then add a couple of eBPF programs that are testing those calls.
The first one checks for valid access, and the second one is OK from a static analysis point of view but fails at run time because we are trying to access outside of the allocated memory.
Signed-off-by: Benjamin Tissoires benjamin.tissoires@redhat.com
CI is failing for test_progs-no_alu32: https://github.com/kernel-patches/bpf/runs/8220916615?check_suite_focus=true
changes in v11:
- use new way of declaring tests
changes in v10:
- use new definitions for tests in an array
- add a new kfunc syscall_test_null_fail test
no changes in v9
no changes in v8
changes in v7:
- add 1 more case to ensure we can read the entire sizeof(ctx)
- add a test case for when the context is NULL
new in v6
net/bpf/test_run.c | 1 + .../selftests/bpf/prog_tests/kfunc_call.c | 143 +++++++++++++++++- .../selftests/bpf/progs/kfunc_call_fail.c | 39 +++++ .../selftests/bpf/progs/kfunc_call_test.c | 38 +++++ 4 files changed, 214 insertions(+), 7 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/kfunc_call_fail.c
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index 25d8ecf105aa..f16baf977a21 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -1634,6 +1634,7 @@ static int __init bpf_prog_test_run_init(void)
ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &bpf_prog_test_kfunc_set); ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_prog_test_kfunc_set);
ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &bpf_prog_test_kfunc_set); return ret ?: register_btf_id_dtor_kfuncs(bpf_prog_test_dtor_kfunc, ARRAY_SIZE(bpf_prog_test_dtor_kfunc), THIS_MODULE);
diff --git a/tools/testing/selftests/bpf/prog_tests/kfunc_call.c b/tools/testing/selftests/bpf/prog_tests/kfunc_call.c index 9dfbe5355a2d..d5881c3331a8 100644 --- a/tools/testing/selftests/bpf/prog_tests/kfunc_call.c +++ b/tools/testing/selftests/bpf/prog_tests/kfunc_call.c @@ -2,6 +2,7 @@ /* Copyright (c) 2021 Facebook */ #include <test_progs.h> #include <network_helpers.h> +#include "kfunc_call_fail.skel.h" #include "kfunc_call_test.skel.h" #include "kfunc_call_test.lskel.h" #include "kfunc_call_test_subprog.skel.h" @@ -10,37 +11,96 @@
#include "cap_helpers.h"
+static size_t log_buf_sz = 1048576; /* 1 MB */ +static char obj_log_buf[1048576];
+enum kfunc_test_type {
tc_test = 0,
syscall_test,
syscall_null_ctx_test,
+};
struct kfunc_test_params { const char *prog_name; unsigned long lskel_prog_desc_offset; int retval;
enum kfunc_test_type test_type;
const char *expected_err_msg;
};
-#define TC_TEST(name, __retval) \ +#define __BPF_TEST_SUCCESS(name, __retval, type) \ { \ .prog_name = #name, \ .lskel_prog_desc_offset = offsetof(struct kfunc_call_test_lskel, progs.name), \ .retval = __retval, \
.test_type = type, \
.expected_err_msg = NULL, \
}
+#define __BPF_TEST_FAIL(name, __retval, type, error_msg) \
{ \
.prog_name = #name, \
.lskel_prog_desc_offset = 0 /* unused when test is failing */, \
.retval = __retval, \
.test_type = type, \
.expected_err_msg = error_msg, \ }
+#define TC_TEST(name, retval) __BPF_TEST_SUCCESS(name, retval, tc_test) +#define SYSCALL_TEST(name, retval) __BPF_TEST_SUCCESS(name, retval, syscall_test) +#define SYSCALL_NULL_CTX_TEST(name, retval) __BPF_TEST_SUCCESS(name, retval, syscall_null_ctx_test)
+#define SYSCALL_NULL_CTX_FAIL(name, retval, error_msg) \
__BPF_TEST_FAIL(name, retval, syscall_null_ctx_test, error_msg)
static struct kfunc_test_params kfunc_tests[] = {
/* failure cases:
* if retval is 0 -> the program will fail to load and the error message is an error
* if retval is not 0 -> the program can be loaded but running it will gives the
* provided return value. The error message is thus the one
* from a successful load
*/
SYSCALL_NULL_CTX_FAIL(kfunc_syscall_test_fail, -EINVAL, "processed 4 insns"),
SYSCALL_NULL_CTX_FAIL(kfunc_syscall_test_null_fail, -EINVAL, "processed 4 insns"),
/* success cases */ TC_TEST(kfunc_call_test1, 12), TC_TEST(kfunc_call_test2, 3), TC_TEST(kfunc_call_test_ref_btf_id, 0),
SYSCALL_TEST(kfunc_syscall_test, 0),
SYSCALL_NULL_CTX_TEST(kfunc_syscall_test_null, 0),
+};
+struct syscall_test_args {
__u8 data[16];
size_t size;
};
static void verify_success(struct kfunc_test_params *param) { struct kfunc_call_test_lskel *lskel = NULL;
LIBBPF_OPTS(bpf_test_run_opts, topts); struct bpf_prog_desc *lskel_prog; struct kfunc_call_test *skel; struct bpf_program *prog; int prog_fd, err;
LIBBPF_OPTS(bpf_test_run_opts, topts,
.data_in = &pkt_v4,
.data_size_in = sizeof(pkt_v4),
.repeat = 1,
);
struct syscall_test_args args = {
.size = 10,
};
switch (param->test_type) {
case syscall_test:
topts.ctx_in = &args;
topts.ctx_size_in = sizeof(args);
/* fallthrough */
case syscall_null_ctx_test:
break;
case tc_test:
topts.data_in = &pkt_v4;
topts.data_size_in = sizeof(pkt_v4);
topts.repeat = 1;
break;
} /* first test with normal libbpf */ skel = kfunc_call_test__open_and_load();
@@ -79,6 +139,72 @@ static void verify_success(struct kfunc_test_params *param) kfunc_call_test_lskel__destroy(lskel); }
+static void verify_fail(struct kfunc_test_params *param) +{
LIBBPF_OPTS(bpf_object_open_opts, opts);
LIBBPF_OPTS(bpf_test_run_opts, topts);
struct bpf_program *prog;
struct kfunc_call_fail *skel;
int prog_fd, err;
struct syscall_test_args args = {
.size = 10,
};
opts.kernel_log_buf = obj_log_buf;
opts.kernel_log_size = log_buf_sz;
opts.kernel_log_level = 1;
switch (param->test_type) {
case syscall_test:
topts.ctx_in = &args;
topts.ctx_size_in = sizeof(args);
/* fallthrough */
case syscall_null_ctx_test:
break;
case tc_test:
topts.data_in = &pkt_v4;
topts.data_size_in = sizeof(pkt_v4);
break;
topts.repeat = 1;
}
skel = kfunc_call_fail__open_opts(&opts);
if (!ASSERT_OK_PTR(skel, "kfunc_call_fail__open_opts"))
goto cleanup;
prog = bpf_object__find_program_by_name(skel->obj, param->prog_name);
if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))
goto cleanup;
bpf_program__set_autoload(prog, true);
err = kfunc_call_fail__load(skel);
if (!param->retval) {
/* the verifier is supposed to complain and refuses to load */
if (!ASSERT_ERR(err, "unexpected load success"))
goto out_err;
} else {
/* the program is loaded but must dynamically fail */
if (!ASSERT_OK(err, "unexpected load error"))
goto out_err;
prog_fd = bpf_program__fd(prog);
err = bpf_prog_test_run_opts(prog_fd, &topts);
if (!ASSERT_EQ(err, param->retval, param->prog_name))
goto out_err;
}
+out_err:
if (!ASSERT_OK_PTR(strstr(obj_log_buf, param->expected_err_msg), "expected_err_msg")) {
fprintf(stderr, "Expected err_msg: %s\n", param->expected_err_msg);
fprintf(stderr, "Verifier output: %s\n", obj_log_buf);
}
+cleanup:
kfunc_call_fail__destroy(skel);
+}
static void test_main(void) { int i; @@ -87,7 +213,10 @@ static void test_main(void) if (!test__start_subtest(kfunc_tests[i].prog_name)) continue;
verify_success(&kfunc_tests[i]);
if (!kfunc_tests[i].expected_err_msg)
verify_success(&kfunc_tests[i]);
else
verify_fail(&kfunc_tests[i]); }
}
diff --git a/tools/testing/selftests/bpf/progs/kfunc_call_fail.c b/tools/testing/selftests/bpf/progs/kfunc_call_fail.c new file mode 100644 index 000000000000..4168027f2ab1 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/kfunc_call_fail.c @@ -0,0 +1,39 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2021 Facebook */ +#include <vmlinux.h> +#include <bpf/bpf_helpers.h>
+extern void bpf_kfunc_call_test_mem_len_pass1(void *mem, int len) __ksym;
+struct syscall_test_args {
__u8 data[16];
size_t size;
+};
+SEC("?syscall") +int kfunc_syscall_test_fail(struct syscall_test_args *args) +{
bpf_kfunc_call_test_mem_len_pass1(&args->data, sizeof(*args) + 1);
return 0;
+}
+SEC("?syscall") +int kfunc_syscall_test_null_fail(struct syscall_test_args *args) +{
/* Must be called with args as a NULL pointer
* we do not check for it to have the verifier consider that
* the pointer might not be null, and so we can load it.
*
* So the following can not be added:
*
* if (args)
* return -22;
*/
bpf_kfunc_call_test_mem_len_pass1(args, sizeof(*args));
return 0;
+}
+char _license[] SEC("license") = "GPL"; diff --git a/tools/testing/selftests/bpf/progs/kfunc_call_test.c b/tools/testing/selftests/bpf/progs/kfunc_call_test.c index 5aecbb9fdc68..94c05267e5e7 100644 --- a/tools/testing/selftests/bpf/progs/kfunc_call_test.c +++ b/tools/testing/selftests/bpf/progs/kfunc_call_test.c @@ -92,4 +92,42 @@ int kfunc_call_test_pass(struct __sk_buff *skb) return 0; }
+struct syscall_test_args {
__u8 data[16];
size_t size;
+};
+SEC("syscall") +int kfunc_syscall_test(struct syscall_test_args *args) +{
const int size = args->size;
if (size > sizeof(args->data))
return -7; /* -E2BIG */
Looks like it is due to this. Verifier is confused because: r7 = args->data; r1 = r7;
then it does r1 <<= 32; r1 >>=32; clearing upper 32 bits, so both r1 and r7 lose the id association which propagates the bounds of r1 learnt from comparison of it with sizeof(args->data);
bpf_kfunc_call_test_mem_len_pass1(&args->data, sizeof(args->data));
bpf_kfunc_call_test_mem_len_pass1(&args->data, sizeof(*args));
Later llvm assigns r7 to r2 for this call's 2nd arg. At this point the verifier still thinks r7 is unbounded, while to make a call with mem, len pair you need non-negative min value.
Easiest way might be to just do args->size & sizeof(args->data), as the verifier log says. You might still keep the error above. Others may have better ideas/insights.
I just did s/const int size/const long size/ to fix the issues.
Also fixed commit in patch 3 that talks about max_ctx_offset and did:
BTF_KFUNC_SET_MAX_CNT = 64,
BTF_KFUNC_SET_MAX_CNT = 256,
and applied.
Great!
Many thanks to both of you for your time and getting me there :)
Cheers, Benjamin