xfrm: Fix memory leak of aead algorithm name

BugLink: https://bugs.launchpad.net/bugs/1878232

commit b5884793 upstream.

commit 1a6509d9 ("[IPSEC]: Add support for combined mode algorithms")
introduced aead. The function attach_aead kmemdup()s the algorithm
name during xfrm_state_construct().
However this memory is never freed.
Implementation has since been slightly modified in
commit ee5c2317 ("xfrm: Clone states properly on migration")
without resolving this leak.
This patch adds a kfree() call for the aead algorithm name.

Fixes: 1a6509d9 ("[IPSEC]: Add support for combined mode algorithms")
Signed-off-by: Ilan Tayari <ilant@mellanox.com>
Acked-by: Rami Rosen <roszenrami@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ian May <ian.may@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

net/xfrm/xfrm_state.c

@@ -332,6 +332,7 @@ static void xfrm_state_gc_destroy(struct xfrm_state *x)
 {
 	tasklet_hrtimer_cancel(&x->mtimer);
 	del_timer_sync(&x->rtimer);
+	kfree(x->aead);
 	kfree(x->aalg);
 	kfree(x->ealg);
 	kfree(x->calg);