Re: [PATCH v3 1/2] liveupdate: prevent double management of files

David Matlack
2026-03-25T20:34:05Z

On Wed, Mar 25, 2026 at 1:20 PM Pratyush Yadav <pratyush@kernel.org> wrote:

> For memfd and hugetlb at least, we serialize the _inode_ not the file.
> The inode has the contents that we care to preserve.
>
> So if two FDs point to the same inode, this will break. You can do this
> by first creating a memfd and then by opening "/proc/self/fd/<fd>". Then
> you would be able to trigger the preservation twice, causing all sorts
> of problems. Same on the retrieve side.

> So unless I am missing something, I don't think this approach will work.
> As much as I hate to suggest it, I think we need to move this check to
> each caller so they can find out the object they need to serialize and
> check if it already is.

I think LUO can still enforce that the file is not preserved twice.
HugeTLB and memfd's preserve() functions just need to also check that
the associated inode has not already been preserved?