SUNRPC: fix gss_auth kref leak in gss_alloc_msg error path

commit dd2fdc3 upstream.

Commit 5940d1c ("SUNRPC: Rebalance a kref in auth_gss.c") added
a kref_get(&gss_auth->kref) call to balance the gss_put_auth() done
in gss_release_msg(), but forgot to add a corresponding kref_put()
on the error path when kstrdup_const() fails.

If service_name is non-NULL and kstrdup_const() fails, the function
jumps to err_put_pipe_version which calls put_pipe_version() and
kfree(gss_msg), but never releases the gss_auth reference. This leads
to a kref leak where the gss_auth structure is never freed.

Add a forward declaration for gss_free_callback() and call kref_put()
in the err_put_pipe_version error path to properly release the
reference taken earlier.

Fixes: 5940d1c ("SUNRPC: Rebalance a kref in auth_gss.c")
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Hodges <git@danielhodges.dev>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: hodgesds

net/sunrpc/auth_gss/auth_gss.c

@@ -39,6 +39,8 @@ static const struct rpc_authops authgss_ops;
 static const struct rpc_credops gss_credops;
 static const struct rpc_credops gss_nullops;
 
+static void gss_free_callback(struct kref *kref);
+
 #define GSS_RETRY_EXPIRED 5
 static unsigned int gss_expired_cred_retry_delay = GSS_RETRY_EXPIRED;
 
@@ -551,6 +553,7 @@ gss_alloc_msg(struct gss_auth *gss_auth,
 	}
 	return gss_msg;
 err_put_pipe_version:
+	kref_put(&gss_auth->kref, gss_free_callback);
 	put_pipe_version(gss_auth->net);
 err_free_msg:
 	kfree(gss_msg);