commit 4a135e53 upstream.

Commit 565f0fa9 ("xfrm: use a dedicated slab cache for struct
xfrm_state") moved xfrm state objects to use their own slab cache.
However, it missed to adapt xfrm_user to use this new cache when
freeing xfrm states.

Fix this by introducing and make use of a new helper for freeing
xfrm_state objects.

Fixes: 565f0fa9 ("xfrm: use a dedicated slab cache for struct xfrm_state")
Reported-by: NPan Bian <bianpan2016@163.com>
Cc: <stable@vger.kernel.org> # v4.18+
Signed-off-by: NMathias Krause <minipli@googlemail.com>
Acked-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>