From: Lorenz Bauer <lmb@cloudflare.com>
Date: Mon, 3 Dec 2018 11:31:23 +0000 (+0000)
Subject: bpf: respect size hint to BPF_PROG_TEST_RUN if present
X-Git-Tag: v5.4-rc1~1957^2~114^2~11^2~3
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=b5a36b1e1b138285ea0df34bf96c759e1e30fafd;p=platform%2Fkernel%2Flinux-rpi.git

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/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 572eb2d..c8e1eee 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -374,8 +374,11 @@ 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 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;
+
+	/* 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, size))
+	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;
 }