From: Michal Privoznik <mprivozn@redhat.com>
Date: Wed, 1 Aug 2018 11:26:46 +0000 (+0200)
Subject: util: Don't overflow in virRandomBits
X-Git-Tag: v4.6.0~5
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=78c47a92ecb450c9f8bcabd35da7006dc2547882;p=thirdparty%2Flibvirt.git

util: Don't overflow in virRandomBits

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@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Pino Toscano <ptoscano@redhat.com>
---

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;
 }