[PATCH] ipv6/sit: fix ipip6_tunnel_get_prl when memory allocation fails

[zys.zljxml@gmail.com]

From: katrinzhou <katrinzhou@tencent.com>

Fix an illegal copy_to_user() attempt when the system fails to
allocate memory for prl due to a lack of memory.

Addresses-Coverity: ("Unused value")
Fixes: 300aaeeaab5f ("[IPV6] SIT: Add SIOCGETPRL ioctl to get/dump PRL.")
Signed-off-by: katrinzhou <katrinzhou@tencent.com>
---
 net/ipv6/sit.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index c0b138c20992..4fb84c0b30be 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -323,8 +323,6 @@ static int ipip6_tunnel_get_prl(struct net_device *dev, struct ip_tunnel_prl __u
 		kcalloc(cmax, sizeof(*kp), GFP_KERNEL_ACCOUNT | __GFP_NOWARN) :
 		NULL;
 
-	rcu_read_lock();
-
 	ca = min(t->prl_count, cmax);
 
 	if (!kp) {
@@ -337,11 +335,12 @@ static int ipip6_tunnel_get_prl(struct net_device *dev, struct ip_tunnel_prl __u
 					      __GFP_NOWARN);
 		if (!kp) {
 			ret = -ENOMEM;
-			goto out;
+			goto err;
 		}
 	}
 
 	c = 0;
+	rcu_read_lock();
 	for_each_prl_rcu(t->prl) {
 		if (c >= cmax)
 			break;
@@ -362,7 +361,7 @@ static int ipip6_tunnel_get_prl(struct net_device *dev, struct ip_tunnel_prl __u
 		ret = -EFAULT;
 
 	kfree(kp);
-
+err:
 	return ret;
 }
 
-- 
2.27.0