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Before enabling idmapped mounts in RHEL the following upstream patches need to backported:

1. https://github.com/torvalds/linux/commit/968219708108440b23bc292e0486e3cc1d9a1bed
2. https://github.com/torvalds/linux/commit/012e332286e2bb9f6ac77d195f17e74b2963d663
3. https://github.com/torvalds/linux/commit/168f912893407a5acb798a4a58613b5f1f98c717
4. https://github.com/torvalds/linux/commit/bf1ac16edf6770a92bc75cf2373f1f9feea398a4
5. https://github.com/torvalds/linux/commit/42d0c4bdf753063b6eec55415003184d3ca24f6e
6. https://github.com/torvalds/linux/commit/d1c56bfdaca465bd1d0e913053a9c5cafe8b6a6c

All of these should already exist in the different LTS releases upstream.

Once these patches have been backported we can think about how to enable idmapped mounts (with a sysctl or not).

After talking with upstream I was pointed to a branch which already contains all patches for 5.14: https://github.com/brauner/linux-pidfd/commits/vfs.idmapped.backport.v5.14

> https://github.com/torvalds/linux/commit/d1c56bfdaca465bd1d0e913053a9c5cafe8b6a6c

This patch should be backported along with MR[1] as they conflict. After backporting the fixes, I will add this patch to MR[1] which allows idmapped mounts.

[1] https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/2179

(In reply to Alexey Gladkov from comment #2)
> > https://github.com/torvalds/linux/commit/d1c56bfdaca465bd1d0e913053a9c5cafe8b6a6c
> 
> This patch should be backported along with MR[1] as they conflict. After
> backporting the fixes, I will add this patch to MR[1] which allows idmapped
> mounts.
> 
> [1]
> https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/
> merge_requests/2179

Good idea.

@cye can I get qa_ack+ ?

Thanks!

Namespace function test pass with 5.14.0-291.2207_819415434.el9.x86_64:
https://beaker.engineering.redhat.com/jobs/7684079

Set verified:tested.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (Important: kernel security, bug fix, and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2023:6583