From 2cd55ac4fd423e53a1554f5a9e0765c1d2fd509e Mon Sep 17 00:00:00 2001
From: Damien Miller <djm@cvs.openbsd.org>
Date: Wed, 15 Oct 2008 03:30:58 +0000
Subject: kernel/5592: yield() between copying out large chunks of random data
 to userspace - mitigates an effective DoS since generating these can hog the
 CPU at splhigh()

feedback & ok tedu@ deraadt@
---
 sys/dev/rnd.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/sys/dev/rnd.c b/sys/dev/rnd.c
index d8d62fa92b7..9bb08acc845 100644
--- a/sys/dev/rnd.c
+++ b/sys/dev/rnd.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: rnd.c,v 1.94 2008/10/10 20:13:11 deraadt Exp $	*/
+/*	$OpenBSD: rnd.c,v 1.95 2008/10/15 03:30:57 djm Exp $	*/
 
 /*
  * rnd.c -- A strong random number generator
@@ -1057,8 +1057,11 @@ randomread(dev_t dev, struct uio *uio, int ioflag)
 		default:
 			ret = ENXIO;
 		}
-		if (n != 0 && ret == 0)
+		if (n != 0 && ret == 0) {
 			ret = uiomove((caddr_t)buf, n, uio);
+			if (!ret && uio->uio_resid > 0)
+				yield();
+		}
 	}
 
 	free(buf, M_TEMP);
-- 
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