From f7a3585a8bee3d91b1cd57dabd4c2b506afef596 Mon Sep 17 00:00:00 2001
Message-Id: <f7a3585a8bee3d91b1cd57dabd4c2b506afef596@dist-git>
From: Michal Privoznik <mprivozn@redhat.com>
Date: Mon, 21 Jan 2019 09:04:10 -0500
Subject: [PATCH] util: Don't overflow in virRandomBits
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https://bugzilla.redhat.com/show_bug.cgi?id=1667329 (RHEL 7.6.z)
https://bugzilla.redhat.com/show_bug.cgi?id=1652894 (RHEL 7.7)

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>
(cherry picked from commit 78c47a92ecb450c9f8bcabd35da7006dc2547882)
Signed-off-by: John Ferlan <jferlan@redhat.com>
Message-Id: <20190121140412.27804-2-jferlan@redhat.com>
Reviewed-by: Erik Skultety <eskultet@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;
 }
 
-- 
2.21.0