linux-kernel - Re: [PATCH] xen: fix potential integer overflow in queue

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Date:	Mon, 18 Jan 2016 16:38:01 +0000
From:	David Vrabel <david.vrabel@...rix.com>
To:	Insu Yun <wuninsu@...il.com>, <konrad.wilk@...cle.com>,
	<boris.ostrovsky@...cle.com>, <Jennifer.Herbert@...rix.com>,
	<xen-devel@...ts.xenproject.org>, <linux-kernel@...r.kernel.org>
CC:	<taesoo@...ech.edu>, <yeongjin.jang@...ech.edu>, <insu@...ech.edu>,
	<changwoo@...ech.edu>
Subject: Re: [PATCH] xen: fix potential integer overflow in queue_reply

On 18/01/16 16:29, Insu Yun wrote:
> When len is greater than UINT_MAX - sizeof(*rb), in next allocation,
> it can overflow integer range and allocates small size of heap.
> After that, memcpy will overflow the allocated heap.
> Therefore, it needs to check the size of given length.
[...]
> --- a/drivers/xen/xenbus/xenbus_dev_frontend.c
> +++ b/drivers/xen/xenbus/xenbus_dev_frontend.c
> @@ -186,7 +186,7 @@ static int queue_reply(struct list_head *queue, const void *data, size_t len)
>  {
>  	struct read_buffer *rb;
>  
> -	if (len == 0)
> +	if (len == 0 || len >= UINT_MAX - sizeof(*rb))
                               ^^^^^^^^^^^^^^^^^^^^^^
Please check

    len > XENSTORE_PAYLOAD_MAX

instead.

David