Date: Sat, 21 Jan 2012 01:56:49 +0400 From: Andrey Chernov <ache@FreeBSD.ORG> To: Mark Murray <mark@grondar.org>, Mark Murray <markm@FreeBSD.ORG> Cc: svn-src-head@FreeBSD.ORG, David Schultz <das@FreeBSD.ORG>, src-committers@FreeBSD.ORG, svn-src-all@FreeBSD.ORG Subject: Re: svn commit: r230230 - head/sys/dev/random Message-ID: <20120120215649.GA40016@vniz.net> In-Reply-To: <E1RoG98-000DiP-0Y@groundzero.grondar.org> References: <201201162018.q0GKIADK050161@svn.freebsd.org> <20120118061943.GA80874@vniz.net> <E1Rny2A-000C3x-O6@groundzero.grondar.org> <20120120055823.GA28177@vniz.net> <E1RoG98-000DiP-0Y@groundzero.grondar.org>
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On Fri, Jan 20, 2012 at 03:12:53PM +0000, Mark Murray wrote:
> Andrey Chernov writes:
> > > Look at the function random_yarrow_unblock(). Thats where yopu want to
> > > be doing this. This function is where the random device is unblocked
> > > once safely seeded.
> >
> > Thanx for your hint, but I fear one moment using random_yarrow_unblock().
> > It is called under mtx_lock(&random_reseed_mtx) in reseed().
> > And when arc4rand() seeding is called, it uses read_random(), so I see
> > possible deadlock can happens.
>
> The usual way round this is with a flag. Set a static, volatile flag, defaulting
> "off", and set it to "on" when the seeding has happened. Then arc4random() can
> do the right thing, depending on this flag.
Ok, what about this version, is it right? libkern/arc4rand.c is not
a module but always present in the kernel, so "arc4rand_iniseed_state" will be
always accessible.
--- dev/random/randomdev_soft.c.old 2011-09-26 07:35:48.000000000 +0400
+++ dev/random/randomdev_soft.c 2012-01-21 01:41:37.000000000 +0400
@@ -55,6 +55,8 @@ __FBSDID("$FreeBSD: src/sys/dev/random/r
#define RANDOM_FIFO_MAX 256 /* How many events to queue up */
+extern int arc4rand_iniseed_state;
+
static void random_kthread(void *);
static void
random_harvest_internal(u_int64_t, const void *, u_int,
@@ -361,6 +363,8 @@ random_yarrow_write(void *buf, int count
void
random_yarrow_unblock(void)
{
+ if (arc4rand_iniseed_state == 0)
+ arc4rand_iniseed_state = 1;
if (!random_systat.seeded) {
random_systat.seeded = 1;
selwakeuppri(&random_systat.rsel, PUSER);
--- libkern/arc4random.c.old 2011-09-26 07:37:23.000000000 +0400
+++ libkern/arc4random.c 2012-01-21 01:46:53.000000000 +0400
@@ -24,6 +24,8 @@ __FBSDID("$FreeBSD: src/sys/libkern/arc4
#define ARC4_RESEED_SECONDS 300
#define ARC4_KEYBYTES (256 / 8)
+int arc4rand_iniseed_state = 0;
+
static u_int8_t arc4_i, arc4_j;
static int arc4_numruns = 0;
static u_int8_t arc4_sbox[256];
@@ -130,10 +132,13 @@ arc4rand(void *ptr, u_int len, int resee
struct timeval tv;
getmicrouptime(&tv);
- if (reseed ||
+ if (reseed || arc4rand_iniseed_state == 1 ||
(arc4_numruns > ARC4_RESEED_BYTES) ||
- (tv.tv_sec > arc4_t_reseed))
+ (tv.tv_sec > arc4_t_reseed)) {
+ if (arc4rand_iniseed_state == 1)
+ arc4rand_iniseed_state = -1;
arc4_randomstir();
+ }
mtx_lock(&arc4_mtx);
arc4_numruns += len;
--
http://ache.vniz.net/
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