svcrpc: don't leak contexts on PROC_DESTROY

BugLink: http://bugs.launchpad.net/bugs/1660993

commit 78794d18 upstream.

Context expiry times are in units of seconds since boot, not unix time.

The use of get_seconds() here therefore sets the expiry time decades in
the future.  This prevents timely freeing of contexts destroyed by
client RPC_GSS_PROC_DESTROY requests.  We'd still free them eventually
(when the module is unloaded or the container shut down), but a lot of
contexts could pile up before then.

Fixes: c5b29f88 "sunrpc: use seconds since boot in expiry cache"
Reported-by: Andy Adamson <andros@netapp.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

net/sunrpc/auth_gss/svcauth_gss.c

@@ -1481,7 +1481,7 @@ svcauth_gss_accept(struct svc_rqst *rqstp, __be32 *authp)
 	case RPC_GSS_PROC_DESTROY:
 		if (gss_write_verf(rqstp, rsci->mechctx, gc->gc_seq))
 			goto auth_err;
-		rsci->h.expiry_time = get_seconds();
+		rsci->h.expiry_time = seconds_since_boot();
 		set_bit(CACHE_NEGATIVE, &rsci->h.flags);
 		if (resv->iov_len + 4 > PAGE_SIZE)
 			goto drop;