Re: [PATCH v2 0/3] pidfd: add task path ioctls

[Chen Linxuan]

On Fri, Sep 4, 2026 at 10:53 PM Florian Weimer <fweimer@xxxxxxxxxx> wrote:
>
> * Chen Linxuan via:
>
> > This series adds PIDFD_GET_EXE, PIDFD_GET_CWD, and PIDFD_GET_ROOT. Each
> > ioctl takes no argument and returns a close-on-exec O_PATH file
> > descriptor referencing the corresponding task path.  The new ioctls use
> > the same ptrace permission check and nonzero-argument rejection as the
> > existing pidfd namespace ioctls.
>
> How would one upgrade the O_PATH descriptor to a full descriptor without
> a mounted /proc?

For PIDFD_GET_CWD and PIDFD_GET_ROOT, the returned O_PATH descriptor is
typically used directly as a base directory for openat(2) or passed to
fchdir(2), so upgrading it to a full descriptor is usually unnecessary.

For cases where upgrading an O_PATH descriptor to a full descriptor is
required without /proc mounted (such as inspecting the executable binary
from PIDFD_GET_EXE), users can use the newly added O_EMPTYPATH flag with
openat2(2) (introduced in Linux 7.2) to reopen the O_PATH descriptor.

>
> Thanks,
> Florian
>
>