9p: fix use after free

On 7/22/07, Adrian Bunk <bunk@stusta.de> wrote:
     The Coverity checker spotted the following use-after-free
     in net/9p/mux.c:

     <--  snip  -->

     ...
     struct p9_conn *p9_conn_create(struct p9_transport *trans, int msize,
                                         unsigned char *extended)
     {
     ...
             if (!m->tagpool) {
                     kfree(m);
                     return ERR_PTR(PTR_ERR(m->tagpool));
             }
     ...

     <--  snip  -->

Also spotted was a leak of the same structure further down in the function.
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

net/9p/mux.c

@@ -288,9 +288,10 @@ struct p9_conn *p9_conn_create(struct p9_transport *trans, int msize,
 	m->extended = extended;
 	m->trans = trans;
 	m->tagpool = p9_idpool_create();
-	if (!m->tagpool) {
+	if (IS_ERR(m->tagpool)) {
+		mtmp = ERR_PTR(-ENOMEM);
 		kfree(m);
-		return ERR_PTR(PTR_ERR(m->tagpool));
+		return mtmp;
 	}
 
 	m->err = 0;
@@ -308,8 +309,10 @@ struct p9_conn *p9_conn_create(struct p9_transport *trans, int msize,
 	memset(&m->poll_waddr, 0, sizeof(m->poll_waddr));
 	m->poll_task = NULL;
 	n = p9_mux_poll_start(m);
-	if (n)
+	if (n) {
+		kfree(m);
 		return ERR_PTR(n);
+	}
 
 	n = trans->poll(trans, &m->pt);
 	if (n & POLLIN) {