Re: [PATCH bpf-next 2/2] selftests/bpf: Add test for resizing data map with struct_ops

[Andrii Nakryiko]

On Wed, Jul 24, 2024 at 10:15 AM David Vernet <void@xxxxxxxxxxxxx> wrote:
>
> Tests that if you resize a map after opening a skel, that it doesn't
> cause a UAF which causes a struct_ops map to fail to be able to load.
>
> Signed-off-by: David Vernet <void@xxxxxxxxxxxxx>
> ---
>  .../bpf/prog_tests/struct_ops_resize.c        | 30 +++++++++++++++++++
>  .../selftests/bpf/progs/struct_ops_resize.c   | 24 +++++++++++++++
>  2 files changed, 54 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/struct_ops_resize.c
>  create mode 100644 tools/testing/selftests/bpf/progs/struct_ops_resize.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/struct_ops_resize.c b/tools/testing/selftests/bpf/prog_tests/struct_ops_resize.c
> new file mode 100644
> index 000000000000..7584f91c2bd1
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/struct_ops_resize.c
> @@ -0,0 +1,30 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <test_progs.h>
> +#include "struct_ops_resize.skel.h"
> +
> +static void resize_datasec(void)
> +{
> +       struct struct_ops_resize *skel;
> +       int err;
> +
> +       skel = struct_ops_resize__open();
> +       if (!ASSERT_OK_PTR(skel, "struct_ops_resize__open"))
> +               return;
> +
> +       err  = bpf_map__set_value_size(skel->maps.data_resizable, 1 << 15);
> +       if (!ASSERT_OK(err, "bpf_map__set_value_size"))
> +               goto cleanup;
> +
> +       err = struct_ops_resize__load(skel);
> +       ASSERT_OK(err, "struct_ops_resize__load");
> +
> +cleanup:
> +       struct_ops_resize__destroy(skel);
> +}
> +
> +void test_struct_ops_resize(void)
> +{
> +       if (test__start_subtest("resize_datasec"))
> +               resize_datasec();

It seems a bit unnecessary to add an entire new test with a subtest
just for this. Would you mind adding this testing logic into the
already existing prog_tests/global_map_resize.c set of cases?

I've applied patch #1, as it's obviously correct, so I didn't want to
delay the fix. Thanks!

> +}
> diff --git a/tools/testing/selftests/bpf/progs/struct_ops_resize.c b/tools/testing/selftests/bpf/progs/struct_ops_resize.c
> new file mode 100644
> index 000000000000..d0b235f4bbaa
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/struct_ops_resize.c
> @@ -0,0 +1,24 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +
> +char _license[] SEC("license") = "GPL";
> +
> +char resizable[1] SEC(".data.resizable");
> +
> +SEC("struct_ops/test_1")
> +int BPF_PROG(test_1)
> +{
> +       return 0;
> +}
> +
> +struct bpf_testmod_ops {
> +       int (*test_1)(void);
> +};
> +
> +SEC(".struct_ops.link")
> +struct bpf_testmod_ops testmod = {
> +       .test_1 = (void *)test_1
> +};
> --
> 2.45.2
>