linux-kernel - Re: [PATCH v3 1/1] io_uring: add a sysctl to disable io

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Date:   Wed, 26 Jul 2023 10:45:49 -0700
From:   Andres Freund <andres@...razel.de>
To:     Matteo Rizzo <matteorizzo@...gle.com>
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        io-uring@...r.kernel.org, axboe@...nel.dk, asml.silence@...il.com,
        corbet@....net, akpm@...ux-foundation.org, keescook@...omium.org,
        ribalda@...omium.org, rostedt@...dmis.org, jannh@...gle.com,
        chenhuacai@...nel.org, gpiccoli@...lia.com, ldufour@...ux.ibm.com,
        evn@...gle.com, poprdi@...gle.com, jordyzomer@...gle.com,
        jmoyer@...hat.com, krisman@...e.de
Subject: Re: [PATCH v3 1/1] io_uring: add a sysctl to disable io_uring
 system-wide

Hi,

On 2023-06-30 15:10:03 +0000, Matteo Rizzo wrote:
> Introduce a new sysctl (io_uring_disabled) which can be either 0, 1,
> or 2. When 0 (the default), all processes are allowed to create io_uring
> instances, which is the current behavior. When 1, all calls to
> io_uring_setup fail with -EPERM unless the calling process has
> CAP_SYS_ADMIN. When 2, calls to io_uring_setup fail with -EPERM
> regardless of privilege.

Hm, is there a chance that instead of requiring CAP_SYS_ADMIN, a certain group
could be required (similar to hugetlb_shm_group)? Requiring CAP_SYS_ADMIN
could have the unintended consequence of io_uring requiring tasks being run
with more privileges than needed... Or some other more granular way of
granting the right to use io_uring?

ISTM that it'd be nice if e.g. a systemd service specification could allow
some services to use io_uring, without allowing it for everyone, or requiring
to run services effectively as root.

Greetings,

Andres Freund