[PATCH 5.10 09/43] net: Implement missing getsockopt(SO_TIMESTAMPING_NEW)

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

5.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jörn-Thorben Hinz <jthinz@mailbox.tu-berlin.de>

[ Upstream commit 7f6ca95d16b96567ce4cf458a2790ff17fa620c3 ]

Commit 9718475e6908 ("socket: Add SO_TIMESTAMPING_NEW") added the new
socket option SO_TIMESTAMPING_NEW. Setting the option is handled in
sk_setsockopt(), querying it was not handled in sk_getsockopt(), though.

Following remarks on an earlier submission of this patch, keep the old
behavior of getsockopt(SO_TIMESTAMPING_OLD) which returns the active
flags even if they actually have been set through SO_TIMESTAMPING_NEW.

The new getsockopt(SO_TIMESTAMPING_NEW) is stricter, returning flags
only if they have been set through the same option.

Fixes: 9718475e6908 ("socket: Add SO_TIMESTAMPING_NEW")
Link: https://lore.kernel.org/lkml/20230703175048.151683-1-jthinz@mailbox.tu-berlin.de/
Link: https://lore.kernel.org/netdev/0d7cddc9-03fa-43db-a579-14f3e822615b@app.fastmail.com/
Signed-off-by: Jörn-Thorben Hinz <jthinz@mailbox.tu-berlin.de>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/core/sock.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index a069b5476df46..9c3bc24bfdd1f 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1383,9 +1383,16 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
 		break;
 
 	case SO_LINGER:
+	case SO_TIMESTAMPING_NEW:
 		lv		= sizeof(v.ling);
-		v.ling.l_onoff	= sock_flag(sk, SOCK_LINGER);
-		v.ling.l_linger	= sk->sk_lingertime / HZ;
+		/* For the later-added case SO_TIMESTAMPING_NEW: Be strict about only
+		 * returning the flags when they were set through the same option.
+		 * Don't change the beviour for the old case SO_TIMESTAMPING_OLD.
+		 */
+		if (optname == SO_TIMESTAMPING_OLD || sock_flag(sk, SOCK_TSTAMP_NEW)) {
+			v.ling.l_onoff	= sock_flag(sk, SOCK_LINGER);
+			v.ling.l_linger	= sk->sk_lingertime / HZ;
+		}
 		break;
 
 	case SO_BSDCOMPAT:
-- 
2.43.0