linux-kernel - Re: [PATCH 28/32] nsfs: support exhaustive file handles

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAOQ4uxhW-pfC8+FSZfvA63mM+Kv1oYOvtzV+KxLycrie1sqdXA@mail.gmail.com>
Date: Wed, 10 Sep 2025 19:07:22 +0200
From: Amir Goldstein <amir73il@...il.com>
To: Christian Brauner <brauner@...nel.org>
Cc: Jan Kara <jack@...e.cz>, 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 28/32] nsfs: support exhaustive file handles

On Wed, Sep 10, 2025 at 4:39 PM Christian Brauner <brauner@...nel.org> wrote:
>
> Pidfd file handles are exhaustive meaning they don't require a handle on
> another pidfd to pass to open_by_handle_at() so it can derive the
> filesystem to decode in. Instead it can be derived from the file
> handle itself. The same is possible for namespace file handles.
>
> Signed-off-by: Christian Brauner <brauner@...nel.org>

Reviewed-by: Amir Goldstein <amir73il@...il.com>


> ---
>  fs/fhandle.c               |  6 ++++++
>  fs/internal.h              |  1 +
>  fs/nsfs.c                  | 10 ++++++++++
>  include/uapi/linux/fcntl.h |  1 +
>  4 files changed, 18 insertions(+)
>
> diff --git a/fs/fhandle.c b/fs/fhandle.c
> index 7c236f64cdea..f18c855bb0c2 100644
> --- a/fs/fhandle.c
> +++ b/fs/fhandle.c
> @@ -11,6 +11,7 @@
>  #include <linux/personality.h>
>  #include <linux/uaccess.h>
>  #include <linux/compat.h>
> +#include <linux/nsfs.h>
>  #include "internal.h"
>  #include "mount.h"
>
> @@ -189,6 +190,11 @@ static int get_path_anchor(int fd, struct path *root)
>                 return 0;
>         }
>
> +       if (fd == FD_NSFS_ROOT) {
> +               nsfs_get_root(root);
> +               return 0;
> +       }
> +
>         return -EBADF;
>  }
>
> diff --git a/fs/internal.h b/fs/internal.h
> index 38e8aab27bbd..a33d18ee5b74 100644
> --- a/fs/internal.h
> +++ b/fs/internal.h
> @@ -355,3 +355,4 @@ int anon_inode_getattr(struct mnt_idmap *idmap, const struct path *path,
>  int anon_inode_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
>                        struct iattr *attr);
>  void pidfs_get_root(struct path *path);
> +void nsfs_get_root(struct path *path);
> diff --git a/fs/nsfs.c b/fs/nsfs.c
> index a1585a2f4f03..3c6fcf652633 100644
> --- a/fs/nsfs.c
> +++ b/fs/nsfs.c
> @@ -25,6 +25,14 @@
>
>  static struct vfsmount *nsfs_mnt;
>
> +static struct path nsfs_root_path = {};
> +
> +void nsfs_get_root(struct path *path)
> +{
> +       *path = nsfs_root_path;
> +       path_get(path);
> +}
> +
>  static long ns_ioctl(struct file *filp, unsigned int ioctl,
>                         unsigned long arg);
>  static const struct file_operations ns_file_operations = {
> @@ -616,4 +624,6 @@ void __init nsfs_init(void)
>         if (IS_ERR(nsfs_mnt))
>                 panic("can't set nsfs up\n");
>         nsfs_mnt->mnt_sb->s_flags &= ~SB_NOUSER;
> +       nsfs_root_path.mnt = nsfs_mnt;
> +       nsfs_root_path.dentry = nsfs_mnt->mnt_root;
>  }
> diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h
> index f291ab4f94eb..3741ea1b73d8 100644
> --- a/include/uapi/linux/fcntl.h
> +++ b/include/uapi/linux/fcntl.h
> @@ -111,6 +111,7 @@
>  #define PIDFD_SELF_THREAD_GROUP                -10001 /* Current thread group leader. */
>
>  #define FD_PIDFS_ROOT                  -10002 /* Root of the pidfs filesystem */
> +#define FD_NSFS_ROOT                   -10003 /* Root of the nsfs filesystem */
>  #define FD_INVALID                     -10009 /* Invalid file descriptor: -10000 - EBADF = -10009 */
>
>  /* Generic flags for the *at(2) family of syscalls. */
>
> --
> 2.47.3
>