[libvirt] [PATCH 1/2] util: Don't overflow in virRandomBits
Daniel P. Berrangé
berrange at redhat.com
Wed Aug 1 12:16:04 UTC 2018
On Wed, Aug 01, 2018 at 01:44:32PM +0200, Michal Privoznik wrote:
> The function is supposed to return up to 64bit long integer. In
> order to do that it calls virRandomBytes() to fill the integer
> with random bytes and then masks out everything but requested
> bits. However, when doing that it shifts 1U and not 1ULL. So
> effectively, requesting 32 random bis or more always return 0
> which is not random enough.
>
> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> ---
> src/util/virrandom.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/src/util/virrandom.c b/src/util/virrandom.c
> index 01cc82a052..3c011a8615 100644
> --- a/src/util/virrandom.c
> +++ b/src/util/virrandom.c
> @@ -68,7 +68,7 @@ uint64_t virRandomBits(int nbits)
> return 0;
> }
>
> - ret &= (1U << nbits) - 1;
> + ret &= (1ULL << nbits) - 1;
> return ret;
> }
Reviewed-by: Daniel P. Berrangé <berrange at redhat.com>
Regards,
Daniel
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