linux-kernel - Re: [PATCH v17 4/5] random: introduce generic vDSO getrandom() implementation

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Message-ID: <CALCETrVQtQO87U3SEgQyHfkNKsrcS8PjeZrsy2MPAU7gQY70XA@mail.gmail.com>
Date: Mon, 17 Jun 2024 17:06:22 -0700
From: Andy Lutomirski <luto@...capital.net>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: linux-kernel@...r.kernel.org, patches@...ts.linux.dev, tglx@...utronix.de, 
	linux-crypto@...r.kernel.org, linux-api@...r.kernel.org, x86@...nel.org, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Adhemerval Zanella Netto <adhemerval.zanella@...aro.org>, "Carlos O'Donell" <carlos@...hat.com>, 
	Florian Weimer <fweimer@...hat.com>, Arnd Bergmann <arnd@...db.de>, Jann Horn <jannh@...gle.com>, 
	Christian Brauner <brauner@...nel.org>, David Hildenbrand <dhildenb@...hat.com>
Subject: Re: [PATCH v17 4/5] random: introduce generic vDSO getrandom() implementation

On Fri, Jun 14, 2024 at 12:08 PM Jason A. Donenfeld <Jason@...c4.com> wrote:
>
> Provide a generic C vDSO getrandom() implementation, which operates on
> an opaque state returned by vgetrandom_alloc() and produces random bytes
> the same way as getrandom(). This has a the API signature:
>
>   ssize_t vgetrandom(void *buffer, size_t len, unsigned int flags, void *opaque_state);

Last time around, I mentioned some potential issues with this function
signature, and I didn't see any answer.  My specific objection was to
the fact that the caller passes in a pointer but not a length, and
this potentially makes reasoning about memory safety awkward,
especially if anything like CRIU is involved.

--Andy