On Mon, 2024-06-24 at 11:49 -0400, Josef Bacik wrote:
> In order to utilize the listmount() and statmount() extensions that
> allow us to call them on different namespaces we need a way to get
> the
> mnt namespace id from user space. Add an ioctl to nsfs that will
> allow
> us to extract the mnt namespace id in order to make these new
> extensions
> usable.
>
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
> ---
> fs/nsfs.c | 14 ++++++++++++++
> include/uapi/linux/nsfs.h | 2 ++
> 2 files changed, 16 insertions(+)
>
> diff --git a/fs/nsfs.c b/fs/nsfs.c
> index 07e22a15ef02..af352dadffe1 100644
> --- a/fs/nsfs.c
> +++ b/fs/nsfs.c
> @@ -12,6 +12,7 @@
> #include <linux/nsfs.h>
> #include <linux/uaccess.h>
>
> +#include "mount.h"
> #include "internal.h"
>
> static struct vfsmount *nsfs_mnt;
> @@ -143,6 +144,19 @@ static long ns_ioctl(struct file *filp, unsigned
> int ioctl,
> argp = (uid_t __user *) arg;
> uid = from_kuid_munged(current_user_ns(), user_ns-
> >owner);
> return put_user(uid, argp);
> + case NS_GET_MNTNS_ID: {
> + struct mnt_namespace *mnt_ns;
> + __u64 __user *idp;
> + __u64 id;
> +
> + if (ns->ops->type != CLONE_NEWNS)
> + return -EINVAL;
> +
> + mnt_ns = container_of(ns, struct mnt_namespace, ns);
> + idp = (__u64 __user *)arg;
> + id = mnt_ns->seq;
> + return put_user(id, idp);
> + }
> default:
> return -ENOTTY;
> }
> diff --git a/include/uapi/linux/nsfs.h b/include/uapi/linux/nsfs.h
> index a0c8552b64ee..56e8b1639b98 100644
> --- a/include/uapi/linux/nsfs.h
> +++ b/include/uapi/linux/nsfs.h
> @@ -15,5 +15,7 @@
> #define NS_GET_NSTYPE _IO(NSIO, 0x3)
> /* Get owner UID (in the caller's user namespace) for a user
> namespace */
> #define NS_GET_OWNER_UID _IO(NSIO, 0x4)
> +/* Get the id for a mount namespace */
> +#define NS_GET_MNTNS_ID _IO(NSIO, 0x5)
>
> #endif /* __LINUX_NSFS_H */
Thinking about this more...
Would it also make sense to wire up a similar ioctl in pidfs? It seems
like it might be nice to just open a pidfd for pid and then issue the
above to get its mntns id, rather than having to grovel around in nsfs.
--
Jeff Layton <jlayton@xxxxxxxxxx>
