From: Willem de Bruijn <willemb@google.com>
Date: Thu, 10 Aug 2017 16:41:58 +0000 (-0400)
Subject: packet: fix tp_reserve race in packet_set_ring
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=fe1fd359c1dbde1c1561802f62a16ddc67c9ac07;p=GitHub%2Fmt8127%2Fandroid_kernel_alcatel_ttab.git

packet: fix tp_reserve race in packet_set_ring

commit c27927e372f0785f3303e8fad94b85945e2c97b7 upstream.

Updates to tp_reserve can race with reads of the field in
packet_set_ring. Avoid this by holding the socket lock during
updates in setsockopt PACKET_RESERVE.

This bug was discovered by syzkaller.

Fixes: 8913336a7e8d ("packet: add PACKET_RESERVE sockopt")
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index b915d0112874..2f22b0759f2c 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3183,14 +3183,19 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv
 
 		if (optlen != sizeof(val))
 			return -EINVAL;
-		if (po->rx_ring.pg_vec || po->tx_ring.pg_vec)
-			return -EBUSY;
 		if (copy_from_user(&val, optval, sizeof(val)))
 			return -EFAULT;
 		if (val > INT_MAX)
 			return -EINVAL;
-		po->tp_reserve = val;
-		return 0;
+		lock_sock(sk);
+		if (po->rx_ring.pg_vec || po->tx_ring.pg_vec) {
+			ret = -EBUSY;
+		} else {
+			po->tp_reserve = val;
+			ret = 0;
+		}
+		release_sock(sk);
+		return ret;
 	}
 	case PACKET_LOSS:
 	{