[bpf-next,3/3] selftests/bpf: test freplace from user namespace

Commit Message

Mykyta Yatsenko March 4, 2025, 9:15 p.m. UTC

From: Mykyta Yatsenko <[e-mail]>

Add selftests to verify that it is possible to load freplace program
from user namespace if BPF token is initialized by bpf_object__prepare
before calling bpf_program__set_attach_target.
Negative test is added as well.

Signed-off-by: Mykyta Yatsenko <[e-mail]>
---
 .../testing/selftests/bpf/prog_tests/token.c  | 94 +++++++++++++++++++
 .../selftests/bpf/progs/priv_freplace_prog.c  | 13 +++
 tools/testing/selftests/bpf/progs/priv_prog.c |  4 +-
 3 files changed, 109 insertions(+), 2 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/priv_freplace_prog.c

Comments

Andrii Nakryiko March 4, 2025, 10:24 p.m. UTC | #1

On Tue, Mar 4, 2025 at 1:15 PM Mykyta Yatsenko
<[e-mail]> wrote:
>
> From: Mykyta Yatsenko <[e-mail]>
>
> Add selftests to verify that it is possible to load freplace program
> from user namespace if BPF token is initialized by bpf_object__prepare
> before calling bpf_program__set_attach_target.
> Negative test is added as well.
>
> Signed-off-by: Mykyta Yatsenko <[e-mail]>
> ---
>  .../testing/selftests/bpf/prog_tests/token.c  | 94 +++++++++++++++++++
>  .../selftests/bpf/progs/priv_freplace_prog.c  | 13 +++
>  tools/testing/selftests/bpf/progs/priv_prog.c |  4 +-
>  3 files changed, 109 insertions(+), 2 deletions(-)
>  create mode 100644 tools/testing/selftests/bpf/progs/priv_freplace_prog.c

[...]

> +/* Verify that freplace works from user namespace, because bpf token is loaded
> + * in bpf_object__prepare
> + */
> +static int userns_obj_priv_freplace_prog(int mnt_fd, struct token_lsm *lsm_skel)
> +{
> +       struct priv_freplace_prog *fr_skel = NULL;
> +       struct priv_prog *skel = NULL;
> +       int err, tgt_fd;
> +
> +       err = userns_obj_priv_freplace_setup(mnt_fd, &fr_skel, &skel, &tgt_fd);
> +       if (!ASSERT_OK(err, "setup"))
> +               goto out;
> +
> +       err = bpf_object__prepare(fr_skel->obj);
> +       if (!ASSERT_OK(err, "freplace__prepare"))
> +               goto out;
> +
> +       err = bpf_program__set_attach_target(fr_skel->progs.new_kprobe_prog, tgt_fd, "kprobe_prog");
> +       if (err)

if (!ASSERT_OK(err, "set_attach_target"))

> +               goto out;
> +
> +       err = priv_freplace_prog__load(fr_skel);
> +       ASSERT_OK(err, "priv_freplace_prog__load");
> +out:
> +       priv_freplace_prog__destroy(fr_skel);
> +       priv_prog__destroy(skel);
> +       return err;
> +}
> +

[...]

> diff --git a/tools/testing/selftests/bpf/progs/priv_prog.c b/tools/testing/selftests/bpf/progs/priv_prog.c
> index 3c7b2b618c8a..be9deda38b52 100644
> --- a/tools/testing/selftests/bpf/progs/priv_prog.c
> +++ b/tools/testing/selftests/bpf/progs/priv_prog.c
> @@ -1,5 +1,5 @@
>  // SPDX-License-Identifier: GPL-2.0
> -/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
> +/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */

you don't need to update copyright year when updating the file, just
leave it as is here and above

>
>  #include "vmlinux.h"
>  #include <bpf/bpf_helpers.h>
> @@ -7,7 +7,7 @@
>  char _license[] SEC("license") = "GPL";
>
>  SEC("kprobe")
> -int kprobe_prog(void *ctx)
> +int kprobe_prog(struct pt_regs *ctx)
>  {
>         return 1;
>  }
> --
> 2.48.1
>

Patch

diff --git a/tools/testing/selftests/bpf/prog_tests/token.c b/tools/testing/selftests/bpf/prog_tests/token.c
index c3ab9b6fb069..38f405b8a2c5 100644
--- a/tools/testing/selftests/bpf/prog_tests/token.c
+++ b/tools/testing/selftests/bpf/prog_tests/token.c
@@ -19,6 +19,7 @@ 
 #include "priv_prog.skel.h"
 #include "dummy_st_ops_success.skel.h"
 #include "token_lsm.skel.h"
+#include "priv_freplace_prog.skel.h"
 
 static inline int sys_mount(const char *dev_name, const char *dir_name,
 			    const char *type, unsigned long flags,
@@ -788,6 +789,83 @@  static int userns_obj_priv_prog(int mnt_fd, struct token_lsm *lsm_skel)
 	return 0;
 }
 
+static int userns_obj_priv_freplace_setup(int mnt_fd, struct priv_freplace_prog **fr_skel,
+					  struct priv_prog **skel, int *tgt_fd)
+{
+	LIBBPF_OPTS(bpf_object_open_opts, opts);
+	int err;
+	char buf[256];
+
+	/* use bpf_token_path to provide BPF FS path */
+	snprintf(buf, sizeof(buf), "/proc/self/fd/%d", mnt_fd);
+	opts.bpf_token_path = buf;
+	*skel = priv_prog__open_opts(&opts);
+	if (!ASSERT_OK_PTR(*skel, "priv_prog__open_opts"))
+		return -EINVAL;
+	err = priv_prog__load(*skel);
+	if (!ASSERT_OK(err, "priv_prog__load"))
+		return -EINVAL;
+
+	*fr_skel = priv_freplace_prog__open_opts(&opts);
+	if (!ASSERT_OK_PTR(*skel, "priv_freplace_prog__open_opts"))
+		return -EINVAL;
+
+	*tgt_fd = bpf_program__fd((*skel)->progs.kprobe_prog);
+	return 0;
+}
+
+/* Verify that freplace works from user namespace, because bpf token is loaded
+ * in bpf_object__prepare
+ */
+static int userns_obj_priv_freplace_prog(int mnt_fd, struct token_lsm *lsm_skel)
+{
+	struct priv_freplace_prog *fr_skel = NULL;
+	struct priv_prog *skel = NULL;
+	int err, tgt_fd;
+
+	err = userns_obj_priv_freplace_setup(mnt_fd, &fr_skel, &skel, &tgt_fd);
+	if (!ASSERT_OK(err, "setup"))
+		goto out;
+
+	err = bpf_object__prepare(fr_skel->obj);
+	if (!ASSERT_OK(err, "freplace__prepare"))
+		goto out;
+
+	err = bpf_program__set_attach_target(fr_skel->progs.new_kprobe_prog, tgt_fd, "kprobe_prog");
+	if (err)
+		goto out;
+
+	err = priv_freplace_prog__load(fr_skel);
+	ASSERT_OK(err, "priv_freplace_prog__load");
+out:
+	priv_freplace_prog__destroy(fr_skel);
+	priv_prog__destroy(skel);
+	return err;
+}
+
+/* Verify that replace fails to set attach target from user namespace without bpf token */
+static int userns_obj_priv_freplace_prog_fail(int mnt_fd, struct token_lsm *lsm_skel)
+{
+	struct priv_freplace_prog *fr_skel = NULL;
+	struct priv_prog *skel = NULL;
+	int err, tgt_fd;
+
+	err = userns_obj_priv_freplace_setup(mnt_fd, &fr_skel, &skel, &tgt_fd);
+	if (!ASSERT_OK(err, "setup"))
+		goto out;
+
+	err = bpf_program__set_attach_target(fr_skel->progs.new_kprobe_prog, tgt_fd, "kprobe_prog");
+	if (ASSERT_ERR(err, "attach fails"))
+		err = 0;
+	else
+		err = -EINVAL;
+
+out:
+	priv_freplace_prog__destroy(fr_skel);
+	priv_prog__destroy(skel);
+	return err;
+}
+
 /* this test is called with BPF FS that doesn't delegate BPF_BTF_LOAD command,
  * which should cause struct_ops application to fail, as BTF won't be uploaded
  * into the kernel, even if STRUCT_OPS programs themselves are allowed
@@ -1010,6 +1088,22 @@  void test_token(void)
 
 		subtest_userns(&opts, userns_obj_priv_prog);
 	}
+	if (test__start_subtest("obj_priv_freplace_prog")) {
+		struct bpffs_opts opts = {
+			.cmds = bit(BPF_BTF_LOAD) | bit(BPF_PROG_LOAD),
+			.progs = bit(BPF_PROG_TYPE_KPROBE) | bit(BPF_PROG_TYPE_EXT),
+			.attachs = ~0ULL,
+		};
+		subtest_userns(&opts, userns_obj_priv_freplace_prog);
+	}
+	if (test__start_subtest("obj_priv_freplace_prog_fail")) {
+		struct bpffs_opts opts = {
+			.cmds = bit(BPF_BTF_LOAD) | bit(BPF_PROG_LOAD),
+			.progs = bit(BPF_PROG_TYPE_KPROBE) | bit(BPF_PROG_TYPE_EXT),
+			.attachs = ~0ULL,
+		};
+		subtest_userns(&opts, userns_obj_priv_freplace_prog_fail);
+	}
 	if (test__start_subtest("obj_priv_btf_fail")) {
 		struct bpffs_opts opts = {
 			/* disallow BTF loading */
diff --git a/tools/testing/selftests/bpf/progs/priv_freplace_prog.c b/tools/testing/selftests/bpf/progs/priv_freplace_prog.c
new file mode 100644
index 000000000000..c9ab81988624
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/priv_freplace_prog.c
@@ -0,0 +1,13 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+char _license[] SEC("license") = "GPL";
+
+SEC("freplace/kprobe_prog")
+int new_kprobe_prog(struct pt_regs *ctx)
+{
+	return 1;
+}
diff --git a/tools/testing/selftests/bpf/progs/priv_prog.c b/tools/testing/selftests/bpf/progs/priv_prog.c
index 3c7b2b618c8a..be9deda38b52 100644
--- a/tools/testing/selftests/bpf/progs/priv_prog.c
+++ b/tools/testing/selftests/bpf/progs/priv_prog.c
@@ -1,5 +1,5 @@ 
 // SPDX-License-Identifier: GPL-2.0
-/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
+/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
 
 #include "vmlinux.h"
 #include <bpf/bpf_helpers.h>
@@ -7,7 +7,7 @@ 
 char _license[] SEC("license") = "GPL";
 
 SEC("kprobe")
-int kprobe_prog(void *ctx)
+int kprobe_prog(struct pt_regs *ctx)
 {
 	return 1;
 }