linux-kernel - Re: [PATCH] Ceph: Fix use-after-free bug in ceph_messenger

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Message-ID: <AANLkTi=O=rKgXMBgMDRFZCCUSkqvHhZ+DkstSzWASVfQ@mail.gmail.com>
Date:	Sat, 25 Dec 2010 22:14:30 +0100
From:	richard -rw- weinberger <richard.weinberger@...il.com>
To:	Jesper Juhl <jj@...osbits.net>
Cc:	ceph-devel@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Sage Weil <sage@...dream.net>
Subject: Re: [PATCH] Ceph: Fix use-after-free bug in ceph_messenger_destroy()

On Sat, Dec 25, 2010 at 7:11 PM, Jesper Juhl <jj@...osbits.net> wrote:
> Hi,
>
> In net/ceph/messenger.c::ceph_messenger_destroy() the pointer 'msgr' is
> freed by kfree() and subsequently used in a call to dout() - use after
> free bug.

As I sad before, %p reads only the address.

> Easily fixed by simply moving the kfree() call after the dout() call.
>
> Signed-off-by: Jesper Juhl <jj@...osbits.net>
> ---
>  messenger.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
> index b6ff4a1..26514a7 100644
> --- a/net/ceph/messenger.c
> +++ b/net/ceph/messenger.c
> @@ -2131,8 +2131,8 @@ void ceph_messenger_destroy(struct ceph_messenger *msgr)
>        dout("destroy %p\n", msgr);
>        kunmap(msgr->zero_page);
>        __free_page(msgr->zero_page);
> -       kfree(msgr);
>        dout("destroyed messenger %p\n", msgr);
> +       kfree(msgr);
>  }
>  EXPORT_SYMBOL(ceph_messenger_destroy);
>
>
> --
> 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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