netdev - [PATCH bpf-next v8 04/12] bpf: Only reply field should be writeable

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Message-ID: <20180124075802.1522053-5-brakmo@fb.com>
Date:   Tue, 23 Jan 2018 23:57:54 -0800
From:   Lawrence Brakmo <brakmo@...com>
To:     netdev <netdev@...r.kernel.org>
CC:     Kernel Team <kernel-team@...com>, Blake Matheny <bmatheny@...com>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>
Subject: [PATCH bpf-next v8 04/12] bpf: Only reply field should be writeable

Currently, a sock_ops BPF program can write the op field and all the
reply fields (reply and replylong). This is a bug. The op field should
not have been writeable and there is currently no way to use replylong
field for indices >= 1. This patch enforces that only the reply field
(which equals replylong[0]) is writeable.

Fixes: 40304b2a1567 ("bpf: BPF support for sock_ops")
Signed-off-by: Lawrence Brakmo <brakmo@...com>
---
 net/core/filter.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 0cf170f..c356ec0 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3845,8 +3845,7 @@ static bool sock_ops_is_valid_access(int off, int size,
 {
 	if (type == BPF_WRITE) {
 		switch (off) {
-		case offsetof(struct bpf_sock_ops, op) ...
-		     offsetof(struct bpf_sock_ops, replylong[3]):
+		case offsetof(struct bpf_sock_ops, reply):
 			break;
 		default:
 			return false;
-- 
2.9.5