From: Lawrence Brakmo <brakmo@fb.com>
Date: Fri, 26 Jan 2018 00:14:05 +0000 (-0800)
Subject: bpf: Only reply field should be writeable
X-Git-Tag: v4.16-rc1~123^2~33^2~5^2~11
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=2585cd62f0986a6e6d9c83363ed6dbcc66bc9f32;p=linux.git

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@fb.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---

diff --git a/net/core/filter.c b/net/core/filter.c
index 18da42a81d0c..bf9bb755e369 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;