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

[David Vrabel <david.vrabel@xxxxxxxxxx>]

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

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