netdev - Re: [PATCH net-next 3/6] random32: add prandom_reseed_late() and call when nonblocking pool becomes initialized

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Message-ID: <20131112130946.GC14929@order.stressinduktion.org>
Date:	Tue, 12 Nov 2013 14:09:46 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Karl Beldan <karl.beldan@...il.com>
Cc:	Johannes Berg <johannes@...solutions.net>,
	Theodore Ts'o <tytso@....edu>,
	Daniel Borkmann <dborkman@...hat.com>, davem@...emloft.net,
	shemminger@...workplumber.org, fweimer@...hat.com,
	netdev@...r.kernel.org, Eric Dumazet <eric.dumazet@...il.com>,
	linux-wireless@...r.kernel.org
Subject: Re: [PATCH net-next 3/6] random32: add prandom_reseed_late() and call when nonblocking pool becomes initialized

On Tue, Nov 12, 2013 at 12:13:10PM +0100, Karl Beldan wrote:
> On Tue, Nov 12, 2013 at 09:36:15AM +0100, Johannes Berg wrote:
> > On Tue, 2013-11-12 at 01:37 +0100, Karl Beldan wrote:
> > 
> > > > > 1)  I'm pretty sure, but it would be good to get netdev confirmation,
> > > > > that the call to get_random_bytes() in
> > > > > net/mac80211/rc80211_minstrel.c's init_sample_table() can be replaced
> > > > > by calls to prandom_u32().
> > > > 
> > > > Would make sense. I added wireless-devel to confirm.
> > > > 
> > > > [...]
> > > > [    0.673260] random: rc80211_minstrel_ht_init+0x47/0xaa get_random_bytes called with 3 bits of entropy available
> > > > [    0.674024] random: rc80211_minstrel_ht_init+0x47/0xaa get_random_bytes called with 3 bits of entropy available
> > > > [    0.675012] random: rc80211_minstrel_ht_init+0x47/0xaa get_random_bytes called with 3 bits of entropy available
> > > > [    0.676032] random: rc80211_minstrel_ht_init+0x47/0xaa get_random_bytes called with 3 bits of entropy available
> > > > [    0.677020] random: rc80211_minstrel_ht_init+0x47/0xaa get_random_bytes called with 3 bits of entropy available
> > > > [    0.678011] random: rc80211_minstrel_ht_init+0x47/0xaa get_random_bytes called with 3 bits of entropy available
> > > > [    0.679011] random: rc80211_minstrel_ht_init+0x47/0xaa get_random_bytes called with 3 bits of entropy available
> > > > [...]
> > > > 
> > > > In total 80 calls to get_random_bytes.
> > > > 
> > > 
> > > It is already 8 times what rc80211_minstrel_ht_init uses.
> > > If you could apply on top of:
> > > http://marc.info/?l=linux-wireless&m=138392850030987&w=2
> > > although Johannes has not yet agreed/applied this.
> > 
> > I'll take the patch, I just wanted a more useful commit log :)
> > 
> The commit log still feels very right to me, but I don't want you to go
> grumpy ;) and will reword the log - Hannes, have you staged replacing
> get_random_bytes with prandom_u32 already or can I do it in a reworded
> v2 for minstrel ?

I haven't done that so far. So, go ahead, I would love to see
that. Btw. there is prandom_bytes, which should be a suitable drop-in.

Btw. if the initialization is run later (as in, after the boot process),
the prandom-PRNG will be better seeded.

Thank you,

  Hannes

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