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

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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.
This commit is contained in:
riastradh 2016-05-21 15:27:15 +00:00
parent 2b38f13330
commit 77ebf39786
1 changed files with 15 additions and 2 deletions
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17
sys/kern/kern_rndq.c
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@ -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 @@ rnd_getmore(size_t byteswanted)
{
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. */