netdev - Re: net/9p/mux.c: use-after-free

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Date:	Wed, 25 Jul 2007 13:43:16 -0500
From:	"Eric Van Hensbergen" <ericvh@...il.com>
To:	"Adrian Bunk" <bunk@...sta.de>
Cc:	"Latchesar Ionkov" <lucho@...kov.net>,
	v9fs-developer@...ts.sourceforge.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: net/9p/mux.c: use-after-free

On 7/22/07, Adrian Bunk <bunk@...sta.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  -->
>

I've got a fix for this one:
        if (!m->tagpool) {
                mtmp = ERR_PTR(PTR_ERR(m->tagpool));
                kfree(m);
                return mtmp;
        }

but I was wondering about one of the other returns further down the function:

...
        memset(&m->poll_waddr, 0, sizeof(m->poll_waddr));
        m->poll_task = NULL;
        n = p9_mux_poll_start(m);
        if (n)
                return ERR_PTR(n);

        n = trans->poll(trans, &m->pt);
...

lucho: doesn't that constitute a leak?  Shouldn't we be doing:

        if (n) {
                kfree(m);
                return ERR_PTR(n);
        }

         -eric
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