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Subject: Re: [Qemu-devel] [PATCH] Correctly free nd structure
From: Mark McLoughlin <markmc@redhat.com>
In-Reply-To: <1253220819-2850-1-git-send-email-glommer@redhat.com>
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Date: Fri, 18 Sep 2009 13:17:29 +0100
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To: Glauber Costa <glommer@redhat.com>
Cc: aliguori@us.ibm.com, qemu-devel@nongnu.org

On Thu, 2009-09-17 at 16:53 -0400, Glauber Costa wrote:
> When we "free" a NICInfo structure, we can leak pointers, since we don't do
> much more than setting used = 0.
> 
> We free() the model parameter, but we don't set it to NULL. This means that
> a new user of this structure will see garbage in there. It was not noticed
> before because reusing a NICInfo is not that common, but it can be, for
> users of device pci hotplug.
> 
> A user hit it, described at https://bugzilla.redhat.com/show_bug.cgi?id=524022
> 
> This patch memset's the whole structure, guaranteeing that anyone reusing it
> will see a fresh NICinfo. Also, we free some other strings that are currently
> leaking.
> 
> This codebase is quite old, so this patch should feed all stable trees.
> 
> Signed-off-by: Glauber Costa <glommer@redhat.com>
> ---
>  net.c |    9 +++++++--
>  1 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/net.c b/net.c
> index 340177e..a405895 100644
> --- a/net.c
> +++ b/net.c
> @@ -2804,8 +2804,13 @@ void net_client_uninit(NICInfo *nd)
>  {
>      nd->vlan->nb_guest_devs--;
>      nb_nics--;
> -    nd->used = 0;
> -    free((void *)nd->model);
> +
> +    qemu_free((void *)nd->model);
> +    qemu_free((void *)nd->name);
> +    qemu_free((void *)nd->devaddr);
> +    qemu_free((void *)nd->id);
> +
> +    memset(nd, 0, sizeof(*nd));
>  }
>  

Looks good to me; my patch to port to QemuOpts actually zeros out the
struct during init()

What is the (void *) cast for, though?

Thanks,
Mark.