linux-kernel - Re: [PATCH 1/1] x86: replace RDRAND forced-reseed with simple sanity check

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 3 Aug 2015 13:20:15 -0400
From:	Len Brown <lenb@...nel.org>
To:	Pavel Machek <pavel@....cz>
Cc:	X86 ML <x86@...nel.org>, Linux PM list <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Len Brown <len.brown@...el.com>
Subject: Re: [PATCH 1/1] x86: replace RDRAND forced-reseed with simple sanity check

> If we trust built-in-self-test...
> why do we need to do this at all? We
> should check the return value at every call, anyway...

Yes, we do trust built-in-self-test.
Yes, we do check for errors on on every call, not just here in boot.

The sanity check at boot from the kernel allows Linux to disable
the feature, preventing user-space from thrashing trying to use it.

There is also a line of reasoning that if the circuit is going to fail,
chances are that it will fail immediately.
I have no reason to believe that the circuit will fail in the field
either at run-time or at boot-time.  But that line of reasoning
suggests that O(1 usec) to check at boot is a prudent investment --
it is certainly a better investment per time than may of the other
things Linux does.

thanks,
Len Brown, Intel Open Source Technology Center
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/