bpf: respect size hint to BPF_PROG_TEST_RUN if present
Use data_size_out as a size hint when copying test output to user space.
ENOSPC is returned if the output buffer is too small.
Callers which so far did not set data_size_out are not affected.
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index c89c22c..7663e6a 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -74,8 +74,18 @@ static int bpf_test_finish(const union bpf_attr *kattr,
{
void __user *data_out = u64_to_user_ptr(kattr->test.data_out);
int err = -EFAULT;
+ u32 copy_size = size;
- if (data_out && copy_to_user(data_out, data, size))
+ /* Clamp copy if the user has provided a size hint, but copy the full
+ * buffer if not to retain old behaviour.
+ */
+ if (kattr->test.data_size_out &&
+ copy_size > kattr->test.data_size_out) {
+ copy_size = kattr->test.data_size_out;
+ err = -ENOSPC;
+ }
+
+ if (data_out && copy_to_user(data_out, data, copy_size))
goto out;
if (copy_to_user(&uattr->test.data_size_out, &size, sizeof(size)))
goto out;
@@ -83,7 +93,8 @@ static int bpf_test_finish(const union bpf_attr *kattr,
goto out;
if (copy_to_user(&uattr->test.duration, &duration, sizeof(duration)))
goto out;
- err = 0;
+ if (err != -ENOSPC)
+ err = 0;
out:
return err;
}