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From:   Jeff Moyer <jmoyer@redhat.com>
To:     Gabriel Krisman Bertazi <krisman@suse.de>
Cc:     Matteo Rizzo <matteorizzo@google.com>, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, io-uring@vger.kernel.org,
        jordyzomer@google.com, evn@google.com, poprdi@google.com,
        corbet@lwn.net, axboe@kernel.dk, asml.silence@gmail.com,
        akpm@linux-foundation.org, keescook@chromium.org,
        rostedt@goodmis.org, dave.hansen@linux.intel.com,
        ribalda@chromium.org, chenhuacai@kernel.org, steve@sk2.org,
        gpiccoli@igalia.com, ldufour@linux.ibm.com
Subject: Re: [PATCH 1/1] Add a new sysctl to disable io_uring system-wide
References: <20230627120058.2214509-1-matteorizzo@google.com>
        <20230627120058.2214509-2-matteorizzo@google.com>
        <87ilb7ofv6.fsf@suse.de>
Date:   Wed, 28 Jun 2023 11:59:25 -0400
In-Reply-To: <87ilb7ofv6.fsf@suse.de> (Gabriel Krisman Bertazi's message of
        "Wed, 28 Jun 2023 09:50:37 -0400")
Message-ID: <x49bkgzefxe.fsf@segfault.boston.devel.redhat.com>
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Gabriel Krisman Bertazi <krisman@suse.de> writes:

> Matteo Rizzo <matteorizzo@google.com> writes:
>
>> diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
>> index d85d90f5d000..3c53a238332a 100644
>> --- a/Documentation/admin-guide/sysctl/kernel.rst
>> +++ b/Documentation/admin-guide/sysctl/kernel.rst
>> @@ -450,6 +450,20 @@ this allows system administrators to override the
>>  ``IA64_THREAD_UAC_NOPRINT`` ``prctl`` and avoid logs being flooded.
>>  
>>  
>> +io_uring_disabled
>> +=========================
>> +
>> +Prevents all processes from creating new io_uring instances. Enabling this
>> +shrinks the kernel's attack surface.
>> +
>> += =============================================================
>> +0 All processes can create io_uring instances as normal. This is the default
>> +  setting.
>> +1 io_uring is disabled. io_uring_setup always fails with -EPERM. Existing
>> +  io_uring instances can still be used.
>> += =============================================================
>
> I had an internal request for something like this recently.  If we go
> this route, we could use a intermediary option that limits io_uring
> to root processes only.

This is all regrettable, but this option makes the most sense to me.
Testing for CAP_SYS_ADMIN or CAP_SYS_RAW_IO would work for that third
option, I think.

-Jeff