Re: [PATCH 1/1] Add a new sysctl to disable io_uring system-wide

[Jeff Moyer <jmoyer@redhat.com>]

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