netdev - [PATCH net-next] net: relax SO_TXTIME CAP_NET

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Date:   Thu,  7 May 2020 10:05:39 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Willem de Bruijn <willemb@...gle.com>
Subject: [PATCH net-next] net: relax SO_TXTIME CAP_NET_ADMIN check

Now sch_fq has horizon feature, we want to allow QUIC/UDP applications
to use EDT model so that pacing can be offloaded to the kernel (sch_fq)
or the NIC.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Willem de Bruijn <willemb@...gle.com>
---
 net/core/sock.c | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index b714162213aeae98bfee24d8b457547fe7abab4f..fd85e651ce284b6987f0e8fae94f76ec2c432899 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1152,23 +1152,31 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
 		break;
 
 	case SO_TXTIME:
-		if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)) {
-			ret = -EPERM;
-		} else if (optlen != sizeof(struct sock_txtime)) {
+		if (optlen != sizeof(struct sock_txtime)) {
 			ret = -EINVAL;
+			break;
 		} else if (copy_from_user(&sk_txtime, optval,
 			   sizeof(struct sock_txtime))) {
 			ret = -EFAULT;
+			break;
 		} else if (sk_txtime.flags & ~SOF_TXTIME_FLAGS_MASK) {
 			ret = -EINVAL;
-		} else {
-			sock_valbool_flag(sk, SOCK_TXTIME, true);
-			sk->sk_clockid = sk_txtime.clockid;
-			sk->sk_txtime_deadline_mode =
-				!!(sk_txtime.flags & SOF_TXTIME_DEADLINE_MODE);
-			sk->sk_txtime_report_errors =
-				!!(sk_txtime.flags & SOF_TXTIME_REPORT_ERRORS);
+			break;
 		}
+		/* CLOCK_MONOTONIC is only used by sch_fq, and this packet
+		 * scheduler has enough safe guards.
+		 */
+		if (sk_txtime.clockid != CLOCK_MONOTONIC &&
+		    !ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)) {
+			ret = -EPERM;
+			break;
+		}
+		sock_valbool_flag(sk, SOCK_TXTIME, true);
+		sk->sk_clockid = sk_txtime.clockid;
+		sk->sk_txtime_deadline_mode =
+			!!(sk_txtime.flags & SOF_TXTIME_DEADLINE_MODE);
+		sk->sk_txtime_report_errors =
+			!!(sk_txtime.flags & SOF_TXTIME_REPORT_ERRORS);
 		break;
 
 	case SO_BINDTOIFINDEX:
-- 
2.26.2.526.g744177e7f7-goog