Patch "packet: fix tp_reserve race in packet_set_ring" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

packet: fix tp_reserve race in packet_set_ring

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
packet-fix-tp_reserve-race-in-packet_set_ring.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Willem de Bruijn <[email protected]>
Date: Thu, 10 Aug 2017 12:41:58 -0400
Subject: packet: fix tp_reserve race in packet_set_ring

From: Willem de Bruijn <[email protected]>

[ Upstream commit c27927e372f0785f3303e8fad94b85945e2c97b7 ]

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.

---
 net/packet/af_packet.c |   13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

@@ -3698,14 +3698,19 @@ packet_setsockopt(struct socket *sock, i
 
 		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:
 	{

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/net-avoid-skb_warn_bad_offload-false-positives-on-ufo.patch queue-4.9/packet-fix-tp_reserve-race-in-packet_set_ring.patch queue-4.9/udp-consistently-apply-ufo-or-fragmentation.patch