Re: [Qemu-devel] [PATCH 5/6] luks: Catch integer overflow for huge sizes

[Eric Blake]

On 03/09/2018 11:27 AM, Kevin Wolf wrote:
> When you request an image size close to UINT64_MAX, the addition of the
> crypto header may cause an integer overflow. Catch it instead of
> silently truncating the image size.
>
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
>   block/crypto.c | 5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/block/crypto.c b/block/crypto.c
> index 4908d8627f..1b46519c53 100644
> --- a/block/crypto.c
> +++ b/block/crypto.c
> @@ -102,6 +102,11 @@ static ssize_t block_crypto_init_func(QCryptoBlock *block,
>   {
>       struct BlockCryptoCreateData *data = opaque;
>   
> +    if (headerlen > UINT64_MAX - data->size) {

INT64_MAX, please.  We are further bounded by having to fit within off_t 
(signed) rather than uint64_t.

> +        error_setg(errp, "The requested file size is too large");
> +        return -EFBIG;
> +    }
> +
>       /* User provided size should reflect amount of space made
>        * available to the guest, so we must take account of that
>        * which will be used by the crypto header

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org