ACK: [SRU][N][PATCH 0/6] proc: restrict overmounting of ephemeral entities

[Ross Porter]

Acked-by: Ross Porter <ross.porter at canonical.com>

On 27/05/2026 12:40, Yufeng Gao wrote:
> BugLink: https://bugs.launchpad.net/bugs/2137199
>
> SRU Justification:
>
> [Impact]
>
> The ability to mount on top of various ephemeral entities in procfs,
> specifically magic links of the form /proc/<pid>/fd/<nr>, causes LTP
> test case mount08 to fail.
>
> [Fix]
>
> Apply the upstream fix:
> https://lore.kernel.org/r/20240806-work-procfs-v1-0-fb04e1d09f0c@kernel.org
>
> The fix prevents overmounting on top of the magic links.
>
> [Test Plan]
>
> Compiled, boot tested and with this patch applied, LTP test case mount08
> passes.
>
> [Where problems could occur]
>
> This is a clean upstream cherry-pick and only prevents mounting on top of
> ephemeral procfs entries which should never be valid mount targets for
> normal usage. Shouldn't break anything else.
>
> Christian Brauner (6):
>    proc: proc_readfd() -> proc_fd_iterate()
>    proc: proc_readfdinfo() -> proc_fdinfo_iterate()
>    proc: add proc_splice_unmountable()
>    proc: block mounting on top of /proc/<pid>/map_files/*
>    proc: block mounting on top of /proc/<pid>/fd/*
>    proc: block mounting on top of /proc/<pid>/fdinfo/*
>
>   fs/proc/base.c     |  4 ++--
>   fs/proc/fd.c       | 16 ++++++++--------
>   fs/proc/internal.h | 13 +++++++++++++
>   3 files changed, 23 insertions(+), 10 deletions(-)
>