[PATCH 1/2] IPv6: Fix the return value of get destination options with NULL data pointer

[Yang Hongyang <yanghy@cn.fujitsu.com>]

If we pass NULL data buffer to getsockopt(), it will return 0,
and the option length is set to -EFAULT:
    getsockopt(sk, IPPROTO_IPV6, IPV6_DSTOPTS, NULL, &len);

This is because ipv6_getsockopt_sticky() will return -EFAULT or
-EINVAL if some error occur.

This patch fix this problem.

Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com> 

---
 net/ipv6/ipv6_sockglue.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index 56d55fe..aa7bedf 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -975,6 +975,9 @@ static int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
 		len = ipv6_getsockopt_sticky(sk, np->opt,
 					     optname, optval, len);
 		release_sock(sk);
+		/* check if ipv6_getsockopt_sticky() returns err code */
+		if (len < 0)
+			return len;
 		return put_user(len, optlen);
 	}
 
-- 1.5.3.8