Merge branch 'prog_test_run-improvement'

Lorenz Bauer says:

====================
Right now, there is no safe way to use BPF_PROG_TEST_RUN with data_out.
This is because bpf_test_finish copies the output buffer to user space
without checking its size. This can lead to the kernel overwriting
data in user space after the buffer if xdp_adjust_head and friends are
in play.

Thanks to everyone for their advice and patience with this patch set!

Changes in v5:
* Fix up libbpf.map

Changes in v4:
* Document bpf_prog_test_run and bpf_prog_test_run_xattr
* Use struct bpf_prog_test_run_attr for return values

Changes in v3:
* Introduce bpf_prog_test_run_xattr instead of modifying the existing
  function

Changes in v2:
* Make the syscall return ENOSPC if data_size_out is too small
* Make bpf_prog_test_run return EINVAL if size_out is missing
* Document the new behaviour of data_size_out
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

3 files changed, 43 insertions, 0 deletions

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index c19226cccf39..5c3be06bf0dd 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -463,6 +463,29 @@ int bpf_prog_test_run(int prog_fd, int repeat, void *data, __u32 size,
 	return ret;
 }
 
+int bpf_prog_test_run_xattr(struct bpf_prog_test_run_attr *test_attr)
+{
+	union bpf_attr attr;
+	int ret;
+
+	if (!test_attr->data_out && test_attr->data_size_out > 0)
+		return -EINVAL;
+
+	bzero(&attr, sizeof(attr));
+	attr.test.prog_fd = test_attr->prog_fd;
+	attr.test.data_in = ptr_to_u64(test_attr->data_in);
+	attr.test.data_out = ptr_to_u64(test_attr->data_out);
+	attr.test.data_size_in = test_attr->data_size_in;
+	attr.test.data_size_out = test_attr->data_size_out;
+	attr.test.repeat = test_attr->repeat;
+
+	ret = sys_bpf(BPF_PROG_TEST_RUN, &attr, sizeof(attr));
+	test_attr->data_size_out = attr.test.data_size_out;
+	test_attr->retval = attr.test.retval;
+	test_attr->duration = attr.test.duration;
+	return ret;
+}
+
 int bpf_prog_get_next_id(__u32 start_id, __u32 *next_id)
 {
 	union bpf_attr attr;
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 60392b70587c..098e6f793b76 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -118,6 +118,25 @@ LIBBPF_API int bpf_prog_attach(int prog_fd, int attachable_fd,
 LIBBPF_API int bpf_prog_detach(int attachable_fd, enum bpf_attach_type type);
 LIBBPF_API int bpf_prog_detach2(int prog_fd, int attachable_fd,
 				enum bpf_attach_type type);
+
+struct bpf_prog_test_run_attr {
+	int prog_fd;
+	int repeat;
+	const void *data_in;
+	__u32 data_size_in;
+	void *data_out;      /* optional */
+	__u32 data_size_out; /* in: max length of data_out
+			      * out: length of data_out */
+	__u32 retval;        /* out: return code of the BPF program */
+	__u32 duration;      /* out: average per repetition in ns */
+};
+
+LIBBPF_API int bpf_prog_test_run_xattr(struct bpf_prog_test_run_attr *test_attr);
+
+/*
+ * bpf_prog_test_run does not check that data_out is large enough. Consider
+ * using bpf_prog_test_run_xattr instead.
+ */
 LIBBPF_API int bpf_prog_test_run(int prog_fd, int repeat, void *data,
 				 __u32 size, void *data_out, __u32 *size_out,
 				 __u32 *retval, __u32 *duration);
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 4fb29f6d7a80..8deff22d61bb 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -65,6 +65,7 @@ LIBBPF_0.0.1 {
 		bpf_prog_load_xattr;
 		bpf_prog_query;
 		bpf_prog_test_run;
+		bpf_prog_test_run_xattr;
 		bpf_program__fd;
 		bpf_program__is_kprobe;
 		bpf_program__is_perf_event;