From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lorenz Bauer Subject: [PATCH 1/3] bpf: respect size hint to BPF_PROG_TEST_RUN if present Date: Fri, 16 Nov 2018 12:53:27 +0000 Message-ID: <20181116125329.3974-2-lmb@cloudflare.com> References: <20181116125329.3974-1-lmb@cloudflare.com> Cc: netdev@vger.kernel.org, linux-api@vger.kernel.org, Lorenz Bauer To: ast@kernel.org, daniel@iogearbox.net Return-path: Received: from mail-wm1-f66.google.com ([209.85.128.66]:33386 "EHLO mail-wm1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727973AbeKPXGF (ORCPT ); Fri, 16 Nov 2018 18:06:05 -0500 Received: by mail-wm1-f66.google.com with SMTP id f19-v6so932218wmb.0 for ; Fri, 16 Nov 2018 04:53:48 -0800 (PST) In-Reply-To: <20181116125329.3974-1-lmb@cloudflare.com> Sender: netdev-owner@vger.kernel.org List-ID: Use data_size_out as a size hint when copying test output to user space. A program using BPF_PERF_OUTPUT can compare its own buffer length with data_size_out after the syscall to detect whether truncation has taken place. Callers which so far did not set data_size_in are not affected. Signed-off-by: Lorenz Bauer --- net/bpf/test_run.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index c89c22c49015..30c57b7f4ba4 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -74,8 +74,15 @@ 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; + + 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; -- 2.17.1