[ 19/27] team: check return value of team_get_port_by_index_rcu() for NULL

[Greg Kroah-Hartman]

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

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

From: Jiri Pirko <jiri@xxxxxxxxxxx>

[ Upstream commit 76c455decbbad31de21c727edb184a963f42b40b ]

team_get_port_by_index_rcu() might return NULL due to race between port
removal and skb tx path. Panic is easily triggeable when txing packets
and adding/removing port in a loop.

introduced by commit 3d249d4ca "net: introduce ethernet teaming device"
and commit 753f993911b "team: introduce random mode" (for random mode)

Signed-off-by: Jiri Pirko <jiri@xxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/team/team_mode_roundrobin.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/net/team/team_mode_roundrobin.c
+++ b/drivers/net/team/team_mode_roundrobin.c
@@ -52,6 +52,8 @@ static bool rr_transmit(struct team *tea
 
 	port_index = rr_priv(team)->sent_packets++ % team->port_count;
 	port = team_get_port_by_index_rcu(team, port_index);
+	if (unlikely(!port))
+		goto drop;
 	port = __get_first_port_up(team, port);
 	if (unlikely(!port))
 		goto drop;


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