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Date:   Tue, 29 May 2018 12:07:43 -0400
From:   "Theodore Y. Ts'o" <tytso@mit.edu>
To:     Prarit Bhargava <prarit@redhat.com>
Cc:     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
Message-ID: <20180529160743.GA7381@thunk.org>
Mail-Followup-To: "Theodore Y. Ts'o" <tytso@mit.edu>,
        Prarit Bhargava <prarit@redhat.com>,
        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>
References: <20180529123800.19627-1-prarit@redhat.com>
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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.

      	     	  	      	   	     - Ted