[PATCH net 2/2] team: reject frames with insufficient headroom in team_header_create

From: Qihang Tang <[email protected]>

AF_PACKET SOCK_DGRAM sends reserve skb headroom from a snapshot of
team_dev->hard_header_len.  A concurrent team type change can switch the
selected port to one with a larger hard_header_len between that snapshot
and team_header_create(), so the port's create() pushes or writes past
skb->head.

This is the same race as in bond_header_create(); the snapshot series
that fixed the SOCK_RAW send paths deferred it.  dev->header_ops is the
stable team_header_ops, so snapshotting header_ops in the caller does
not help.

Reject the frame if skb headroom is smaller than the selected port's
hard_header_len, before delegating under the existing rcu_read_lock.

Fixes: 425000dbf173 ("team: fix header_ops type confusion with non-Ethernet ports")
Cc: [email protected]
Cc: Willem de Bruijn <[email protected]>
Cc: Jiri Pirko <[email protected]>
Signed-off-by: Qihang Tang <[email protected]>
---
 drivers/net/team/team_core.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/net/team/team_core.c b/drivers/net/team/team_core.c
index feaa75fbf8fc..2742a4bfc9d0 100644
--- a/drivers/net/team/team_core.c
+++ b/drivers/net/team/team_core.c
@@ -2269,10 +2269,24 @@ static int team_header_create(struct sk_buff *skb, struct net_device *team_dev,
 	port = team_header_port_get_rcu(team, true);
 	if (port) {
 		port_ops = READ_ONCE(port->dev->header_ops);
-		if (port_ops && port_ops->create)
+		if (port_ops && port_ops->create) {
+			unsigned int hlen = READ_ONCE(port->dev->hard_header_len);
+
+			/* Headroom was reserved from a snapshot of
+			 * team_dev->hard_header_len that may predate this
+			 * port (concurrent team type change); reject if
+			 * insufficient for the port's create(), which
+			 * pushes its own hlen.
+			 */
+			if (skb_headroom(skb) < hlen) {
+				ret = -EINVAL;
+				goto unlock;
+			}
 			ret = port_ops->create(skb, port->dev,
 					       type, daddr, saddr, len);
+		}
 	}
+unlock:
 	rcu_read_unlock();
 	return ret;
 }
-- 
2.50.1 (Apple Git-155)