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Message-ID: <c723f4fd42163e0a701c94e3002127170c5590aa.camel@huaweicloud.com>
Date: Tue, 06 Sep 2022 10:30:19 +0200
From: Roberto Sassu <roberto.sassu@...weicloud.com>
To: Kumar Kartikeya Dwivedi <memxor@...il.com>
Cc: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
martin.lau@...ux.dev, song@...nel.org, yhs@...com,
john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
haoluo@...gle.com, jolsa@...nel.org, mykolal@...com,
dhowells@...hat.com, jarkko@...nel.org, rostedt@...dmis.org,
mingo@...hat.com, paul@...l-moore.com, jmorris@...ei.org,
serge@...lyn.com, shuah@...nel.org, bpf@...r.kernel.org,
keyrings@...r.kernel.org, linux-security-module@...r.kernel.org,
linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
deso@...teo.net, Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [PATCH v16 12/12] selftests/bpf: Add tests for dynamic pointers
parameters in kfuncs
On Tue, 2022-09-06 at 05:15 +0200, Kumar Kartikeya Dwivedi wrote:
> On Mon, 5 Sept 2022 at 16:36, Roberto Sassu
> <roberto.sassu@...weicloud.com> wrote:
> > From: Roberto Sassu <roberto.sassu@...wei.com>
> >
> > Add tests to ensure that only supported dynamic pointer types are
> > accepted,
> > that the passed argument is actually a dynamic pointer, and that
> > the passed
> > argument is a pointer to the stack.
> >
> > The tests are currently in the deny list for s390x (JIT does not
> > support
> > calling kernel function).
> >
> > Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> > ---
> > tools/testing/selftests/bpf/DENYLIST.s390x | 1 +
> > .../bpf/prog_tests/kfunc_dynptr_param.c | 103
> > ++++++++++++++++++
> > .../bpf/progs/test_kfunc_dynptr_param.c | 57 ++++++++++
> > 3 files changed, 161 insertions(+)
> > create mode 100644
> > tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
> > create mode 100644
> > tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c
> >
> > diff --git a/tools/testing/selftests/bpf/DENYLIST.s390x
> > b/tools/testing/selftests/bpf/DENYLIST.s390x
> > index 4e305baa5277..9a6dc3671c65 100644
> > --- a/tools/testing/selftests/bpf/DENYLIST.s390x
> > +++ b/tools/testing/selftests/bpf/DENYLIST.s390x
> > @@ -71,3 +71,4 @@ cgroup_hierarchical_stats # JIT
> > does not support calling kernel f
> > htab_update # failed to attach:
> > ERROR: strerror_r(-
> > 524)=22 (trampoline)
> > lookup_key # JIT does not support
> > calling kernel function (kfunc)
> > verify_pkcs7_sig # JIT does not support
> > calling kernel function (kfunc)
> > +kfunc_dynptr_param # JIT does not support
> > calling kernel function (kfunc)
> > diff --git
> > a/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
> > b/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
> > new file mode 100644
> > index 000000000000..ea655a5c9d8b
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
> > @@ -0,0 +1,103 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +/*
> > + * Copyright (c) 2022 Facebook
> > + * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH
> > + *
> > + * Author: Roberto Sassu <roberto.sassu@...wei.com>
> > + */
> > +
> > +#include <test_progs.h>
> > +#include "test_kfunc_dynptr_param.skel.h"
> > +
> > +static size_t log_buf_sz = 1048576; /* 1 MB */
> > +static char obj_log_buf[1048576];
> > +
> > +static struct {
> > + const char *prog_name;
> > + const char *expected_err_msg;
> > +} kfunc_dynptr_tests[] = {
> > + {"dynptr_type_not_supp",
> > + "arg#0 pointer type STRUCT bpf_dynptr_kern points to
> > unsupported dynamic pointer type"},
> > + {"not_valid_dynptr",
> > + "arg#0 pointer type STRUCT bpf_dynptr_kern must be valid
> > and initialized"},
> > + {"not_ptr_to_stack", "arg#0 pointer type STRUCT
> > bpf_dynptr_kern not to stack"},
> > +};
> > +
> > +static bool kfunc_not_supported;
> > +
> > +static int libbpf_print_cb(enum libbpf_print_level level, const
> > char *fmt,
> > + va_list args)
> > +{
> > + if (strcmp(fmt, "libbpf: extern (func ksym) '%s': not found
> > in kernel or module BTFs\n"))
> > + return 0;
> > +
> > + if (strcmp(va_arg(args, char *),
> > "bpf_verify_pkcs7_signature"))
> > + return 0;
> > +
> > + kfunc_not_supported = true;
> > + return 0;
> > +}
> > +
> > +static void verify_fail(const char *prog_name, const char
> > *expected_err_msg)
> > +{
> > + struct test_kfunc_dynptr_param *skel;
> > + LIBBPF_OPTS(bpf_object_open_opts, opts);
> > + libbpf_print_fn_t old_print_cb;
> > + struct bpf_program *prog;
> > + int err;
> > +
> > + opts.kernel_log_buf = obj_log_buf;
> > + opts.kernel_log_size = log_buf_sz;
> > + opts.kernel_log_level = 1;
> > +
> > + skel = test_kfunc_dynptr_param__open_opts(&opts);
> > + if (!ASSERT_OK_PTR(skel,
> > "test_kfunc_dynptr_param__open_opts"))
> > + goto cleanup;
> > +
> > + prog = bpf_object__find_program_by_name(skel->obj,
> > prog_name);
> > + if (!ASSERT_OK_PTR(prog,
> > "bpf_object__find_program_by_name"))
> > + goto cleanup;
> > +
> > + bpf_program__set_autoload(prog, true);
> > +
> > + bpf_map__set_max_entries(skel->maps.ringbuf,
> > getpagesize());
> > +
> > + kfunc_not_supported = false;
> > +
> > + old_print_cb = libbpf_set_print(libbpf_print_cb);
> > + err = test_kfunc_dynptr_param__load(skel);
> > + libbpf_set_print(old_print_cb);
> > +
> > + if (err < 0 && kfunc_not_supported) {
> > + fprintf(stderr,
> > + "%s:SKIP:bpf_verify_pkcs7_signature() kfunc not
> > supported\n",
> > + __func__);
> > + test__skip();
> > + goto cleanup;
> > + }
> > +
> > + if (!ASSERT_ERR(err, "unexpected load success"))
> > + goto cleanup;
> > +
> > + if (!ASSERT_OK_PTR(strstr(obj_log_buf, expected_err_msg),
> > "expected_err_msg")) {
> > + fprintf(stderr, "Expected err_msg: %s\n",
> > expected_err_msg);
> > + fprintf(stderr, "Verifier output: %s\n",
> > obj_log_buf);
> > + }
> > +
> > +cleanup:
> > + test_kfunc_dynptr_param__destroy(skel);
> > +}
> > +
> > +void test_kfunc_dynptr_param(void)
> > +{
> > + int i;
> > +
> > + for (i = 0; i < ARRAY_SIZE(kfunc_dynptr_tests); i++) {
> > + if
> > (!test__start_subtest(kfunc_dynptr_tests[i].prog_name))
> > + continue;
> > +
> > + verify_fail(kfunc_dynptr_tests[i].prog_name,
> > + kfunc_dynptr_tests[i].expected_err_msg)
> > ;
> > + }
> > +}
> > diff --git
> > a/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c
> > b/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c
> > new file mode 100644
> > index 000000000000..2f09f91a1576
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c
> > @@ -0,0 +1,57 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +/*
> > + * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH
> > + *
> > + * Author: Roberto Sassu <roberto.sassu@...wei.com>
> > + */
> > +
> > +#include "vmlinux.h"
> > +#include <errno.h>
> > +#include <bpf/bpf_helpers.h>
> > +#include <bpf/bpf_tracing.h>
> > +
> > +struct bpf_dynptr {
> > + __u64 :64;
> > + __u64 :64;
> > +} __attribute__((aligned(8)));
> > +
> > +extern int bpf_verify_pkcs7_signature(struct bpf_dynptr *data_ptr,
> > + struct bpf_dynptr *sig_ptr,
> > + struct bpf_key
> > *trusted_keyring) __ksym;
> > +
> > +struct {
> > + __uint(type, BPF_MAP_TYPE_RINGBUF);
> > +} ringbuf SEC(".maps");
> > +
> > +char _license[] SEC("license") = "GPL";
> > +
> > +SEC("?lsm.s/bpf")
> > +int BPF_PROG(dynptr_type_not_supp, int cmd, union bpf_attr *attr,
> > + unsigned int size)
> > +{
> > + char write_data[64] = "hello there, world!!";
> > + struct bpf_dynptr ptr;
> > +
> > + bpf_ringbuf_reserve_dynptr(&ringbuf, sizeof(write_data), 0,
> > &ptr);
> > +
> > + return bpf_verify_pkcs7_signature(&ptr, &ptr, NULL);
> > +}
> > +
> > +SEC("?lsm.s/bpf")
> > +int BPF_PROG(not_valid_dynptr, int cmd, union bpf_attr *attr,
> > unsigned int size)
> > +{
> > + unsigned long val;
> > +
> > + return bpf_verify_pkcs7_signature((struct bpf_dynptr
> > *)&val,
> > + (struct bpf_dynptr
> > *)&val, NULL);
> > +}
> > +
> > +SEC("?lsm.s/bpf")
> > +int BPF_PROG(not_ptr_to_stack, int cmd, union bpf_attr *attr,
> > unsigned int size)
> > +{
> > + unsigned long val;
> > +
> > + return bpf_verify_pkcs7_signature((struct bpf_dynptr *)val,
> > + (struct bpf_dynptr *)val,
> > NULL);
>
> Please also include a test where you cause the dynptr to be set to
> NULL, e.g. by passing invalid stuff to ringbuf_reserve_dynptr, and
> then try to pass it to bpf_verify_pkc7_signature.
Uhm, bpf_ringbuf_reserve_dynptr() is expecting a valid map. How else I
can achieve it?
Thanks
Roberto
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