[PATCH bpf-next v7 04/13] bpf: stop calling some sock_op BPF CALLs in new timestamping callbacks

[Jason Xing <kerneljasonxing@gmail.com>]

Simply disallow calling bpf_sock_ops_setsockopt/getsockopt,
bpf_sock_ops_cb_flags_set, and the bpf_sock_ops_load_hdr_opt for
the new timestamping callbacks for the safety consideration.

Besides, In the next round, we will support the UDP proto for
SO_TIMESTAMPING bpf extension, so we need to ensure there is no
safety problem, which is usually caused by UDP socket trying to
access TCP fields.

Signed-off-by: Jason Xing <kerneljasonxing@gmail.com>
---
 net/core/filter.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/net/core/filter.c b/net/core/filter.c
index dc0e67c5776a..d3395ffe058e 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5523,6 +5523,11 @@ static int __bpf_setsockopt(struct sock *sk, int level, int optname,
 	return -EINVAL;
 }
 
+static bool is_locked_tcp_sock_ops(struct bpf_sock_ops_kern *bpf_sock)
+{
+	return bpf_sock->op <= BPF_SOCK_OPS_WRITE_HDR_OPT_CB;
+}
+
 static int _bpf_setsockopt(struct sock *sk, int level, int optname,
 			   char *optval, int optlen)
 {
@@ -5673,6 +5678,9 @@ static const struct bpf_func_proto bpf_sock_addr_getsockopt_proto = {
 BPF_CALL_5(bpf_sock_ops_setsockopt, struct bpf_sock_ops_kern *, bpf_sock,
 	   int, level, int, optname, char *, optval, int, optlen)
 {
+	if (!is_locked_tcp_sock_ops(bpf_sock))
+		return -EOPNOTSUPP;
+
 	return _bpf_setsockopt(bpf_sock->sk, level, optname, optval, optlen);
 }
 
@@ -5758,6 +5766,9 @@ static int bpf_sock_ops_get_syn(struct bpf_sock_ops_kern *bpf_sock,
 BPF_CALL_5(bpf_sock_ops_getsockopt, struct bpf_sock_ops_kern *, bpf_sock,
 	   int, level, int, optname, char *, optval, int, optlen)
 {
+	if (!is_locked_tcp_sock_ops(bpf_sock))
+		return -EOPNOTSUPP;
+
 	if (IS_ENABLED(CONFIG_INET) && level == SOL_TCP &&
 	    optname >= TCP_BPF_SYN && optname <= TCP_BPF_SYN_MAC) {
 		int ret, copy_len = 0;
@@ -5800,6 +5811,9 @@ BPF_CALL_2(bpf_sock_ops_cb_flags_set, struct bpf_sock_ops_kern *, bpf_sock,
 	struct sock *sk = bpf_sock->sk;
 	int val = argval & BPF_SOCK_OPS_ALL_CB_FLAGS;
 
+	if (!is_locked_tcp_sock_ops(bpf_sock))
+		return -EOPNOTSUPP;
+
 	if (!IS_ENABLED(CONFIG_INET) || !sk_fullsock(sk))
 		return -EINVAL;
 
@@ -7609,6 +7623,9 @@ BPF_CALL_4(bpf_sock_ops_load_hdr_opt, struct bpf_sock_ops_kern *, bpf_sock,
 	u8 search_kind, search_len, copy_len, magic_len;
 	int ret;
 
+	if (!is_locked_tcp_sock_ops(bpf_sock))
+		return -EOPNOTSUPP;
+
 	/* 2 byte is the minimal option len except TCPOPT_NOP and
 	 * TCPOPT_EOL which are useless for the bpf prog to learn
 	 * and this helper disallow loading them also.
-- 
2.43.5