[PATCH] client: disallow unprivileged users to escalate root privileges

[PATCH] client: disallow unprivileged users to escalate root  privileges

An unprivileged user can `chmod 777` a directory owned by root
and gain access. Fix this bug and also add a test case for the
same.

Signed-off-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Venky Shankar <vshankar@redhat.com>
origin: backport, https://github.com/ceph/ceph/commit/b6d85b595ea7c9e0fca10d5e77a48102110fe22c
bug-github-pull: https://github.com/ceph/ceph/pull/60314
bug: https://github.com/ceph/ceph/security/advisories/GHSA-89hm-qq33-2fjm
bug-debian: https://bugs.debian.org/1108410

Gbp-Pq: Name CVE-2025-52555-1.patch