linux-ext4 - Re: Linux 5.3-rc8

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Date:   Mon, 16 Sep 2019 18:23:56 -0700
From:   Matthew Garrett <mjg59@...f.ucam.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        "Ahmed S. Darwish" <darwish.07@...il.com>
CC:     "Theodore Y. Ts'o" <tytso@....edu>, Willy Tarreau <w@....eu>,
        Vito Caputo <vcaputo@...garu.com>,
        Lennart Poettering <mzxreary@...inter.de>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jan Kara <jack@...e.cz>, Ray Strode <rstrode@...hat.com>,
        William Jon McCann <mccann@....edu>,
        "Alexander E. Patrakov" <patrakov@...il.com>,
        zhangjs <zachary@...shancloud.com>, linux-ext4@...r.kernel.org,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: Linux 5.3-rc8

On 16 September 2019 18:05:57 GMT-07:00, Linus Torvalds <torvalds@...ux-foundation.org> wrote:
>On Mon, Sep 16, 2019 at 4:29 PM Ahmed S. Darwish <darwish.07@...il.com>
>wrote:
>>
>> Linus, in all honesty, the other case is _not_ a hypothetical .
>
>Oh yes it is.
>
>You're confusing "use" with "breakage".
>
>The _use_ of getrandom(0) for key generation isn't hypothetical.
>
>But the _breakage_ from the suggested patch that makes it time out is.
>
>See the difference?
>
>The thing is, to break, you have to
>
> (a) do that key generation at boot time
>
> (b) do it on an idle machine that doesn't have entropy

Exactly the scenario where you want getrandom() to block, yes. 

>in order to basically reproduce the current boot-time hang situation
>with the broken gdm, except with an actual "generate key".
>
>Then you have to ignore the big warning too.

The big warning that's only printed in dmesg? 


-- 
Matthew Garrett | mjg59@...f.ucam.org