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From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Yann Droneaud <yann@droneaud.fr>
Cc: linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
	linux-api@vger.kernel.org, Theodore Ts'o <tytso@mit.edu>,
	Andy Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>,
	Carlos O'Donell <carlos@redhat.com>,
	Florian Weimer <fweimer@redhat.com>,
	Arnd Bergmann <arnd@arndb.de>, Jann Horn <jannh@google.com>,
	Christian Brauner <brauner@kernel.org>,
	David Hildenbrand <dhildenb@redhat.com>
Subject: Re: [PATCH] random: vDSO getrandom() must reject invalid flag
Date: Mon, 26 Aug 2024 08:53:00 +0200	[thread overview]
Message-ID: <ZswmTJf1asZUJ-5Z@zx2c4.com> (raw)
In-Reply-To: <20240825144758.325298-1-yann@droneaud.fr>

Hi Yann,

On Sun, Aug 25, 2024 at 04:47:50PM +0200, Yann Droneaud wrote:
> Like getrandom() syscall, vDSO getrandom() must not let
> unknown flags unnoticed [1].
> 
> It could be possible to return -EINVAL from vDSO, but
> in the likely case a new flag is added to getrandom()
> syscall in the future, it would be nicer to get the
> behavior from the syscall, instead of an error until
> the vDSO is extended to support the new flag.

Thanks, that seems right to me.

Currently the @flags only matter if the RNG isn't initialized yet, so we
fallback if it's not initialized. But if it is initialized, all of the
flags behave the same way, so it didn't bother checking them. But that
doesn't account for invalid flags, and you're right to point out that
accepting them silently is an API problem.

I've applied this here, and I'll send it in as a fix soon:

    https://git.kernel.org/pub/scm/linux/kernel/git/crng/random.git/commit/?id=ed9fbbeb29


Thanks for the patch,
Jason

  reply	other threads:[~2024-08-26  6:53 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-07-12  1:40 [PATCH v23 0/4] implement getrandom() in vDSO Jason A. Donenfeld
2024-07-12  1:40 ` [PATCH v23 1/4] mm: add MAP_DROPPABLE for designating always lazily freeable mappings Jason A. Donenfeld
2024-09-12  3:11   ` Miaohe Lin
2024-07-12  1:40 ` [PATCH v23 2/4] random: introduce generic vDSO getrandom() implementation Jason A. Donenfeld
2024-08-25 14:47   ` [PATCH] random: vDSO getrandom() must reject invalid flag Yann Droneaud
2024-08-26  6:53     ` Jason A. Donenfeld [this message]
2024-07-12  1:40 ` [PATCH v23 3/4] x86: vdso: Wire up getrandom() vDSO implementation Jason A. Donenfeld
2024-07-12  1:40 ` [PATCH v23 4/4] selftests/vDSO: add tests for vgetrandom Jason A. Donenfeld

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