Pull vfs fixes from Christian Brauner:
- Don't warn when a mount is completed from another user namespace.
fsopen() records the caller's user namespace in fc->user_ns and
hands back an ordinary file descriptor. The task that calls
fsconfig(FSCONFIG_CMD_CREATE) doesn't have to be the one that
created the context, and mount_capable() lets it through as long
as the caller has CAP_SYS_ADMIN over fc->user_ns, which anyone in
an ancestor namespace does. So fc->user_ns != current_user_ns()
is something an unprivileged user can arrange.
Both overlayfs and binfmt_misc WARN_ON() that. Overlayfs already
has the same check as a plain error return in ovl_parse_param().
Drop the WARN_ON() and just refuse. Add selftests for both cases.
- Reject pid allocations through dead ancestor pid namespaces.
Require PIDNS_ADDING in every namespace that will receive the pid
before publishing any of them. That preserves the invariant that
free_pid() never decrements pid_allocated in a namespace whose
child_reaper is no longer live. The existing ENOMEM behavior is
unchanged.
* tag 'vfs-7.2-rc8.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
pid: reject allocations through dead ancestor pid namespaces
selftests/filesystems: test completing a context from another user namespace
binfmt_misc: don't warn when the mount is completed from another user namespace
ovl: don't warn when the mount is completed from another user namespace
ad8d485e66