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Date: Wed, 7 Sep 2022 04:34:09 +0200
From: Kumar Kartikeya Dwivedi <memxor@...il.com>
To: Roberto Sassu <roberto.sassu@...weicloud.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, 6 Sept 2022 at 10:31, Roberto Sassu
<roberto.sassu@...weicloud.com> wrote:
>
> 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?
So? Just define a ringbuf map and pass to it? I'm missing why that is
undesirable.
It also needs to be a runtime test, not verifier test, I probably
replied to the wrong patch.
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