linux-kernel - Re: [PATCH v2 30/33] nsfs: add missing id retrieval support

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Message-ID: <bmkl6ii7y7fbkzndiukfuxpgsysli6552zzg2fsax4xqhgms73@wk7sfbp6hqyl>
Date: Mon, 15 Sep 2025 15:28:31 +0200
From: Jan Kara <jack@...e.cz>
To: Christian Brauner <brauner@...nel.org>
Cc: Jan Kara <jack@...e.cz>, Amir Goldstein <amir73il@...il.com>, 
	linux-fsdevel@...r.kernel.org, Josef Bacik <josef@...icpanda.com>, 
	Jeff Layton <jlayton@...nel.org>, Mike Yuan <me@...dnzj.com>, 
	Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>, Lennart Poettering <mzxreary@...inter.de>, 
	Daan De Meyer <daan.j.demeyer@...il.com>, Aleksa Sarai <cyphar@...har.com>, 
	Alexander Viro <viro@...iv.linux.org.uk>, Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org>, 
	Johannes Weiner <hannes@...xchg.org>, Michal Koutný <mkoutny@...e.com>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Chuck Lever <chuck.lever@...cle.com>, linux-nfs@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, cgroups@...r.kernel.org, 
	netdev@...r.kernel.org
Subject: Re: [PATCH v2 30/33] nsfs: add missing id retrieval support

On Fri 12-09-25 13:52:53, Christian Brauner wrote:
> The mount namespace has supported id retrieval for a while already.
> Add support for the other types as well.
> 
> Signed-off-by: Christian Brauner <brauner@...nel.org>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/nsfs.c                 | 25 +++++++++++++------------
>  include/uapi/linux/nsfs.h |  6 ++++--
>  2 files changed, 17 insertions(+), 14 deletions(-)
> 
> diff --git a/fs/nsfs.c b/fs/nsfs.c
> index 22765fcab18e..8484bc4dd3de 100644
> --- a/fs/nsfs.c
> +++ b/fs/nsfs.c
> @@ -177,6 +177,7 @@ static bool nsfs_ioctl_valid(unsigned int cmd)
>  	case NS_GET_TGID_FROM_PIDNS:
>  	case NS_GET_PID_IN_PIDNS:
>  	case NS_GET_TGID_IN_PIDNS:
> +	case NS_GET_ID:
>  		return true;
>  	}
>  
> @@ -226,18 +227,6 @@ 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: {
> -		__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->ns.ns_id;
> -		return put_user(id, idp);
> -	}
>  	case NS_GET_PID_FROM_PIDNS:
>  		fallthrough;
>  	case NS_GET_TGID_FROM_PIDNS:
> @@ -283,6 +272,18 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl,
>  			ret = -ESRCH;
>  		return ret;
>  	}
> +	case NS_GET_MNTNS_ID:
> +		if (ns->ops->type != CLONE_NEWNS)
> +			return -EINVAL;
> +		fallthrough;
> +	case NS_GET_ID: {
> +		__u64 __user *idp;
> +		__u64 id;
> +
> +		idp = (__u64 __user *)arg;
> +		id = ns->ns_id;
> +		return put_user(id, idp);
> +	}
>  	}
>  
>  	/* extensible ioctls */
> diff --git a/include/uapi/linux/nsfs.h b/include/uapi/linux/nsfs.h
> index fa86fe3c8bd3..5d5bf22464c9 100644
> --- a/include/uapi/linux/nsfs.h
> +++ b/include/uapi/linux/nsfs.h
> @@ -16,8 +16,6 @@
>  #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		_IOR(NSIO, 0x5, __u64)
>  /* Translate pid from target pid namespace into the caller's pid namespace. */
>  #define NS_GET_PID_FROM_PIDNS	_IOR(NSIO, 0x6, int)
>  /* Return thread-group leader id of pid in the callers pid namespace. */
> @@ -42,6 +40,10 @@ struct mnt_ns_info {
>  /* Get previous namespace. */
>  #define NS_MNT_GET_PREV		_IOR(NSIO, 12, struct mnt_ns_info)
>  
> +/* Retrieve namespace identifiers. */
> +#define NS_GET_MNTNS_ID		_IOR(NSIO, 5,  __u64)
> +#define NS_GET_ID		_IOR(NSIO, 13, __u64)
> +
>  enum init_ns_ino {
>  	IPC_NS_INIT_INO		= 0xEFFFFFFFU,
>  	UTS_NS_INIT_INO		= 0xEFFFFFFEU,
> 
> -- 
> 2.47.3
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR