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@xxxxxxxxxxxxxx>
---
include/uapi/linux/bpf.h | 7 +++++--
net/bpf/test_run.c | 15 +++++++++++++--
2 files changed, 18 insertions(+), 4 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 05d95290b848..7f5a7d032cd1 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -356,8 +356,11 @@ union bpf_attr {
struct { /* anonymous struct used by BPF_PROG_TEST_RUN command */
__u32 prog_fd;
__u32 retval;
- __u32 data_size_in;
- __u32 data_size_out;
+ __u32 data_size_in; /* input: len of data_in */
+ __u32 data_size_out; /* input/output: len of data_out
+ * returns ENOSPC if data_out
+ * is too small.
+ */
__aligned_u64 data_in;
__aligned_u64 data_out;
__u32 repeat;
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index c89c22c49015..7663e6a57280 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;
}
--
2.17.1
