tools/xenstore: fix connection->id usage

Don't use conn->id for privilege checks, but domain_is_unprivileged().

This is part of XSA-326.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit 3047df38e1)

tools/xenstore/xenstored_control.c

@@ -180,7 +180,7 @@ int do_control(struct connection *conn, struct buffered_data *in)
 	int cmd;
 	char **vec;
 
-	if (conn->id != 0)
+	if (domain_is_unprivileged(conn))
 		return EACCES;
 
 	num = xs_count_strings(in->buffer, in->used);

tools/xenstore/xenstored_core.h

@@ -93,7 +93,7 @@ struct connection
 	/* The index of pollfd in global pollfd array */
 	int pollfd_idx;
 
-	/* Who am I? 0 for socket connections. */
+	/* Who am I? Domid of connection. */
 	unsigned int id;
 
 	/* Is this a read-only connection? */

tools/xenstore/xenstored_transaction.c

@@ -483,7 +483,8 @@ int do_transaction_start(struct connection *conn, struct buffered_data *in)
 	if (conn->transaction)
 		return EBUSY;
 
-	if (conn->id && conn->transaction_started > quota_max_transaction)
+	if (domain_is_unprivileged(conn) &&
+	    conn->transaction_started > quota_max_transaction)
 		return ENOSPC;
 
 	/* Attach transaction to input for autofree until it's complete */