[PATCH 3.16.y-ckt 27/71] xfrm: fix a race in xfrm_state_lookup_byspi

[Luis Henriques]

3.16.7-ckt14 -stable review patch.  If anyone has any objections, please let me know.

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

From: Li RongQing <roy.qing.li at gmail.com>

commit bdddbf6996c0b9299efc97b8f66e06286f3aa8c9 upstream.

The returned xfrm_state should be hold before unlock xfrm_state_lock,
otherwise the returned xfrm_state maybe be released.

Fixes: c454997e6[{pktgen, xfrm} Introduce xfrm_state_lookup_byspi..]
Cc: Fan Du <fan.du at intel.com>
Signed-off-by: Li RongQing <roy.qing.li at gmail.com>
Acked-by: Fan Du <fan.du at intel.com>
Signed-off-by: Steffen Klassert <steffen.klassert at secunet.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/xfrm/xfrm_state.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 0ab54134bb40..86f381b09d8d 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -934,8 +934,8 @@ struct xfrm_state *xfrm_state_lookup_byspi(struct net *net, __be32 spi,
 			x->id.spi != spi)
 			continue;
 
-		spin_unlock_bh(&net->xfrm.xfrm_state_lock);
 		xfrm_state_hold(x);
+		spin_unlock_bh(&net->xfrm.xfrm_state_lock);
 		return x;
 	}
 	spin_unlock_bh(&net->xfrm.xfrm_state_lock);