Re: [PATCH] xen: fix potential integer overflow in queue_reply

From: David Vrabel <david.vrabel@citrix.com>
To: David Vrabel <david.vrabel@citrix.com>,
	Insu Yun <wuninsu@gmail.com>,
	konrad.wilk@oracle.com, boris.ostrovsky@oracle.com,
	Jennifer.Herbert@citrix.com, xen-devel@lists.xenproject.org,
	linux-kernel@vger.kernel.org
Cc: yeongjin.jang@gatech.edu, taesoo@gatech.edu, insu@gatech.edu,
	changwoo@gatech.edu
Subject: Re: [PATCH] xen: fix potential integer overflow in queue_reply
Date: Mon, 18 Jan 2016 16:47:15 +0000	[thread overview]
Message-ID: <569D1713.3060306__7389.68908922306$1453135718$gmane$org@citrix.com> (raw)
In-Reply-To: <569D14E9.2050300@citrix.com>

On 18/01/16 16:38, David Vrabel wrote:
> 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.

And return -EINVAL in this case (not zero).

David