netdev - Re: [PATCH] Ceph: Fix a use-after-free bug in ceph_destroy

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Message-ID: <AANLkTik+yrpY8T69w_RQ84ZbRqwkjvFhvxHLBvU14N3f@mail.gmail.com>
Date:	Sat, 25 Dec 2010 22:12:31 +0100
From:	richard -rw- weinberger <richard.weinberger@...il.com>
To:	Jesper Juhl <jj@...osbits.net>
Cc:	ceph-devel@...r.kernel.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, Sage Weil <sage@...dream.net>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] Ceph: Fix a use-after-free bug in ceph_destroy_client().

On Sat, Dec 25, 2010 at 7:17 PM, Jesper Juhl <jj@...osbits.net> 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@...osbits.net>
> ---
>  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@...osbits.net>            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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