[src/trunk]: src/sys/kern Ask on-demand entropy sources to produce enough dat...

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/d062dc3038a9
branches:  trunk
changeset: 345352:d062dc3038a9
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Sat May 21 15:27:15 2016 +0000

description:
Ask on-demand entropy sources to produce enough data to fill buffer.

Remainder of fix for PR kern/51135: if there is an entropy source
that can produce arbitrarily much data, as in rump, then nothing
should ever block indefinitely waiting for data.

diffstat:

 sys/kern/kern_rndq.c |  17 +++++++++++++++--
 1 files changed, 15 insertions(+), 2 deletions(-)

diffs (38 lines):

diff -r d2862611b399 -r d062dc3038a9 sys/kern/kern_rndq.c
--- a/sys/kern/kern_rndq.c      Sat May 21 14:59:45 2016 +0000
+++ b/sys/kern/kern_rndq.c      Sat May 21 15:27:15 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_rndq.c,v 1.88 2016/02/29 01:57:30 riastradh Exp $ */
+/*     $NetBSD: kern_rndq.c,v 1.89 2016/05/21 15:27:15 riastradh Exp $ */
 
 /*-
  * Copyright (c) 1997-2013 The NetBSD Foundation, Inc.
@@ -32,7 +32,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_rndq.c,v 1.88 2016/02/29 01:57:30 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_rndq.c,v 1.89 2016/05/21 15:27:15 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/atomic.h>
@@ -258,6 +258,19 @@
 {
        krndsource_t *rs, *next;
 
+       /*
+        * Due to buffering in rnd_process_events, even if the entropy
+        * sources provide the requested number of bytes, users may not
+        * be woken because the data may be stuck in unfilled buffers.
+        * So ask for enough data to fill all the buffers.
+        *
+        * XXX Just get rid of this buffering and solve the
+        * /dev/random-as-side-channel-for-keystroke-timings a
+        * different way.
+        */
+       byteswanted = MAX(byteswanted,
+           MAX(RND_POOLBITS/NBBY, sizeof(uint32_t)*RND_SAMPLE_COUNT));
+
        mutex_spin_enter(&rnd_global.lock);
        LIST_FOREACH_SAFE(rs, &rnd_global.sources, list, next) {
                /* Skip if the source is disabled.  */