[PATCH bpf-next 03/14] bpf: net: Consider optval.is_bpf before capable check in sock_setsockopt()

[Martin KaFai Lau <kafai@xxxxxx>]

When bpf program calling bpf_setsockopt(SOL_SOCKET),
it could be run in softirq and doesn't make sense to do the capable
check.  There was a similar situation in bpf_setsockopt(TCP_CONGESTION).
In commit 8d650cdedaab ("tcp: fix tcp_set_congestion_control() use from bpf hook")
tcp_set_congestion_control(..., cap_net_admin) was added to skip
the cap check for bpf prog.

A similar change is done in this patch for SO_MARK, SO_PRIORITY,
and SO_BINDTO{DEVICE,IFINDEX} which are the optnames allowed by
bpf_setsockopt(SOL_SOCKET).  This will allow the sock_setsockopt()
to be reused by bpf_setsockopt(SOL_SOCKET) in a latter patch.

Signed-off-by: Martin KaFai Lau <kafai@xxxxxx>
---
 net/core/sock.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index 61d927a5f6cb..f2c582491d5f 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -620,7 +620,7 @@ struct dst_entry *sk_dst_check(struct sock *sk, u32 cookie)
 }
 EXPORT_SYMBOL(sk_dst_check);
 
-static int sock_bindtoindex_locked(struct sock *sk, int ifindex)
+static int sock_bindtoindex_locked(struct sock *sk, int ifindex, bool cap_check)
 {
 	int ret = -ENOPROTOOPT;
 #ifdef CONFIG_NETDEVICES
@@ -628,7 +628,8 @@ static int sock_bindtoindex_locked(struct sock *sk, int ifindex)
 
 	/* Sorry... */
 	ret = -EPERM;
-	if (sk->sk_bound_dev_if && !ns_capable(net->user_ns, CAP_NET_RAW))
+	if (sk->sk_bound_dev_if && cap_check &&
+	    !ns_capable(net->user_ns, CAP_NET_RAW))
 		goto out;
 
 	ret = -EINVAL;
@@ -656,7 +657,7 @@ int sock_bindtoindex(struct sock *sk, int ifindex, bool lock_sk)
 
 	if (lock_sk)
 		lock_sock(sk);
-	ret = sock_bindtoindex_locked(sk, ifindex);
+	ret = sock_bindtoindex_locked(sk, ifindex, true);
 	if (lock_sk)
 		release_sock(sk);
 
@@ -704,7 +705,7 @@ static int sock_setbindtodevice(struct sock *sk, sockptr_t optval, int optlen)
 	}
 
 	lock_sock_sockopt(sk, optval);
-	ret = sock_bindtoindex_locked(sk, index);
+	ret = sock_bindtoindex_locked(sk, index, !optval.is_bpf);
 	release_sock_sockopt(sk, optval);
 out:
 #endif
@@ -1166,6 +1167,7 @@ int sock_setsockopt(struct sock *sk, int level, int optname,
 
 	case SO_PRIORITY:
 		if ((val >= 0 && val <= 6) ||
+		    optval.is_bpf ||
 		    ns_capable(sock_net(sk)->user_ns, CAP_NET_RAW) ||
 		    ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))
 			sk->sk_priority = val;
@@ -1312,7 +1314,8 @@ int sock_setsockopt(struct sock *sk, int level, int optname,
 			clear_bit(SOCK_PASSSEC, &sock->flags);
 		break;
 	case SO_MARK:
-		if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_RAW) &&
+		if (!optval.is_bpf &&
+		    !ns_capable(sock_net(sk)->user_ns, CAP_NET_RAW) &&
 		    !ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)) {
 			ret = -EPERM;
 			break;
@@ -1456,7 +1459,7 @@ int sock_setsockopt(struct sock *sk, int level, int optname,
 		break;
 
 	case SO_BINDTOIFINDEX:
-		ret = sock_bindtoindex_locked(sk, val);
+		ret = sock_bindtoindex_locked(sk, val, !optval.is_bpf);
 		break;
 
 	case SO_BUF_LOCK:
-- 
2.30.2