Re: [PATCH] Ceph: Fix a use-after-free bug in ceph_destroy_client().

[richard -rw- weinberger]

On Sat, Dec 25, 2010 at 7:17 PM, Jesper Juhl <jj@xxxxxxxxxxxxx> wrote:
> Hello,
>
> In net/ceph/ceph_common.c::ceph_destroy_client() the pointer 'client' is
> freed by kfree() and subsequently used in a call to dout() - use after
> free bug.

Not really. %p reads only the address of "client".
kfree() does not alter this address.

> Easily fixed by simply moving the kfree() call after the dout() call.
>
> Signed-off-by: Jesper Juhl <jj@xxxxxxxxxxxxx>
> ---
>  ceph_common.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> diff --git a/net/ceph/ceph_common.c b/net/ceph/ceph_common.c
> index f3e4a13..890bbbf 100644
> --- a/net/ceph/ceph_common.c
> +++ b/net/ceph/ceph_common.c
> @@ -408,8 +408,8 @@ void ceph_destroy_client(struct ceph_client *client)
>
>        ceph_destroy_options(client->options);
>
> -       kfree(client);
>        dout("destroy_client %p done\n", client);
> +       kfree(client);
>  }
>  EXPORT_SYMBOL(ceph_destroy_client);
>
>
> --
> Jesper Juhl <jj@xxxxxxxxxxxxx>            http://www.chaosbits.net/
> Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html
> Plain text mails only, please.
>
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-- 
Thanks,
//richard
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