From 333517ac1c558f36114351193889397712905a85 Mon Sep 17 00:00:00 2001
From: Michael Braun <michael-dev@fami-braun.de>
Date: Fri, 18 Aug 2017 18:55:17 +0200
Subject: [PATCH] crypto: Fix undefined behavior in random number generator

ubsan reported:

../src/crypto/random.c:69:30: runtime error: shift exponent 32 is too large for 32-bit type 'unsigned int'

Explicitly check for the ROL32(x, 0) case which is supposed to be a
no-op.

Signed-off-by: Michael Braun <michael-dev@fami-braun.de>
---
 src/crypto/random.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/crypto/random.c b/src/crypto/random.c
index 3a86a93a4..fb9241762 100644
--- a/src/crypto/random.c
+++ b/src/crypto/random.c
@@ -66,6 +66,9 @@ static void random_write_entropy(void);
 
 static u32 __ROL32(u32 x, u32 y)
 {
+	if (y == 0)
+		return x;
+
 	return (x << (y & 31)) | (x >> (32 - (y & 31)));
 }