Re: [PATCH v3 1/1] io_uring: add a sysctl to disable io_uring system-wide

Andres Freund [off-list ref] writes:

Hi,

Sorry for the delayed response, EINBOXOVERFLOW.

On 2023-07-26 16:02:26 -0400, Jeff Moyer wrote:

quoted

Andres Freund [off-list ref] writes:

quoted

Hi,

On 2023-06-30 15:10:03 +0000, Matteo Rizzo wrote:

quoted

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?

That's fine with me, so long as there is still an option to completely
disable io_uring.

Makes sense.

quoted

quoted

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.

Do you have a proposal for how that would work?

I think group based permissions would allow for it, even if perhaps not in the
most beautiful manner. Systemd can configure additional groups for a service
with SupplementaryGroups, so adding a "io_uring" group or such should
work.

This is more complex/requires more configuration than just blocking
root/non-root. Also, might not be practical for non-systemd systems, I
suspect. Can we keep the other options in the sysctl io_uring_disabled
as well:

0 -> all allowed (default)
1 -> group based permission
2 -> root only
3 -> all blocked

-- 
Gabriel Krisman Bertazi