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

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Message-ID: <AANLkTikw_2ztHC4Q0e=QoJ7RjuAXGpX5u0nTjtbdECXa@mail.gmail.com>
Date:	Sat, 25 Dec 2010 22:16:31 +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,
	Sage Weil <sage@...dream.net>
Subject: Re: [PATCH] Ceph: Fix use-after-free in destroy_fs_client()

On Sat, Dec 25, 2010 at 7:01 PM, Jesper Juhl <jj@...osbits.net> wrote:
> Hi,
>
> In fs/ceph/super.c::destroy_fs_client() the pointer 'fsc' is freed by
> kfree() and subsequently used in a call to dout() - use after free bug.
> Easily fixed by simply moving the kfree() call after the dout() call.

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

> Signed-off-by: Jesper Juhl <jj@...osbits.net>
> ---
>  super.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> diff --git a/fs/ceph/super.c b/fs/ceph/super.c
> index 08b460a..7373594 100644
> --- a/fs/ceph/super.c
> +++ b/fs/ceph/super.c
> @@ -498,8 +498,8 @@ void destroy_fs_client(struct ceph_fs_client *fsc)
>
>        ceph_destroy_client(fsc->client);
>
> -       kfree(fsc);
>        dout("destroy_fs_client %p done\n", fsc);
> +       kfree(fsc);
>  }
>
>  /*
>
>
> --
> 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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