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

[Yufeng Gao]

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(-)

-- 
2.43.0