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bpf: Only reply field should be writeable

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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: 40304b2a15 ("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>
This commit is contained in:
Lawrence Brakmo
2018-01-25 16:14:05 -08:00
committed by Alexei Starovoitov
parent e9dcd80b9d
commit 2585cd62f0
1 changed files with 1 additions and 2 deletions
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3
net/core/filter.c
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@@ -3845,8 +3845,7 @@ static bool sock_ops_is_valid_access(int off, int size,
{ {
if (type == BPF_WRITE) { if (type == BPF_WRITE) {
switch (off) { switch (off) {
case offsetof(struct bpf_sock_ops, op) ... case offsetof(struct bpf_sock_ops, reply):
offsetof(struct bpf_sock_ops, replylong[3]):
break; break;
default: default:
return false; return false;