[PATCH] net: key: af_key: Fix possible null-pointer dereferences in pfkey_send_policy_notify()

[Jia-Ju Bai <baijiaju1990@gmail.com>]

In pfkey_send_policy_notify(), there is an if statement on line 3081 to
check whether xp is NULL:
    if (xp && xp->type != XFRM_POLICY_TYPE_MAIN)

When xp is NULL, it is used by key_notify_policy() on line 3090:
    key_notify_policy(xp, ...)
        pfkey_xfrm_policy2msg_prep(xp) -- line 2211
            pfkey_xfrm_policy2msg_size(xp) -- line 2046
                for (i=0; i<xp->xfrm_nr; i++) -- line 2026
                t = xp->xfrm_vec + i; -- line 2027
    key_notify_policy(xp, ...)
        xp_net(xp) -- line 2231
            return read_pnet(&xp->xp_net); -- line 534

Thus, possible null-pointer dereferences may occur.

To fix these bugs, xp is checked before calling key_notify_policy().

These bugs are found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
 net/key/af_key.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/key/af_key.c b/net/key/af_key.c
index b67ed3a8486c..ced54144d5fd 100644
--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -3087,6 +3087,8 @@ static int pfkey_send_policy_notify(struct xfrm_policy *xp, int dir, const struc
 	case XFRM_MSG_DELPOLICY:
 	case XFRM_MSG_NEWPOLICY:
 	case XFRM_MSG_UPDPOLICY:
+		if (!xp)
+			break;
 		return key_notify_policy(xp, dir, c);
 	case XFRM_MSG_FLUSHPOLICY:
 		if (c->data.type != XFRM_POLICY_TYPE_MAIN)
-- 
2.17.0