[BUG] net: xfrm: possible null-pointer dereferences in xfrm_policy()

[Jia-Ju Bai]

In xfrm_policy(), the while loop on lines 3802-3830 ends when dst->xfrm 
is NULL.
Then, dst->xfrm is used on line 3840:
    xfrm_state_mtu(dst->xfrm, mtu);
        if (x->km.state != XFRM_STATE_VALID...)
        aead = x->data;
Thus, possible null-pointer dereferences may occur.

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

I do not know how to correctly fix these bugs, so I only report them.


Best wishes,
Jia-Ju Bai