From: Prarit Bhargava <prarit@redhat.com>
To: "Theodore Y. Ts'o" <tytso@mit.edu>,
Kees Cook <keescook@chromium.org>,
LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
X86 ML <x86@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Rik van Riel <riel@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Philippe Ombredanne <pombredanne@nexb.com>,
"Jason A. Donenfeld" <Jason@zx2c4.com>,
Kate Stewart <kstewart@linuxfoundation.org>
Subject: Re: [PATCH] x86, random: Fix get_random_bytes() warning in x86 start_kernel
Date: Tue, 29 May 2018 12:58:10 -0400 [thread overview]
Message-ID: <35cdbb04-7b1d-59ae-2ff8-af1d57751113@redhat.com> (raw)
In-Reply-To: <20180529160743.GA7381@thunk.org>
On 05/29/2018 12:07 PM, Theodore Y. Ts'o wrote:
> On Tue, May 29, 2018 at 11:01:07AM -0400, Prarit Bhargava wrote:
>> Kees, in early boot no pool is available so the stack canary is initialized from
>> the TSC. Later in boot, the stack canary will use the the crng.
>>
>> ie) in early boot only TSC is okay, and late boot (when crng_ready() is true)
>> the pool will be used.
>
> But that means all of the kernel threads (e.g., workqueues, et. al)
> would not be well protected by the stack canary. That
> seems.... rather unfortunate.
Well, as stated the TSC is used as a source of entropy in early boot. It's
always been that way and get_random_bytes() AFAICT has always returned 0. CPUs
added later on via hotplug do use get_random_bytes().
Does anyone cc'd have a better idea on how to get another source of entropy this
early in boot?
P.
>
> - Ted
>
next prev parent reply other threads:[~2018-05-29 16:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-29 12:38 Prarit Bhargava
2018-05-29 14:49 ` Kees Cook
2018-05-29 15:01 ` Prarit Bhargava
2018-05-29 16:07 ` Theodore Y. Ts'o
2018-05-29 16:58 ` Prarit Bhargava [this message]
2018-05-29 18:19 ` hpa
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