Re: [libvirt] [PATCH 1/2] util: Don't overflow in virRandomBits

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(a)redhat.com&gt; > --- > 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;