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From: David Howells <dhowells@redhat.com>
To: Andrei Vagin <avagin@virtuozzo.com>
Cc: dhowells@redhat.com, viro@zeniv.linux.org.uk,
	linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org
Subject: Re: [12/24] proc: Add fs_context support to procfs [ver #7]
Date: Tue, 26 Jun 2018 09:57:07 +0100	[thread overview]
Message-ID: <31831.1530003427@warthog.procyon.org.uk> (raw)
In-Reply-To: <20180626072736.GA31860@outlook.office365.com>

Andrei Vagin <avagin@virtuozzo.com> wrote:

> > > > -	mnt = kern_mount_data(&proc_fs_type, ns, 0);
> > 
> > Here ns->user_ns and get_current_cred()->user_ns are not always equal
> 
> What do you think about the attached patch?
> ...
> -	fc = vfs_new_fs_context(&proc_fs_type, NULL, 0,
> -				FS_CONTEXT_FOR_KERNEL_MOUNT);
> +	fc = vfs_new_fs_context_userns(&proc_fs_type, NULL, 0,
> +				FS_CONTEXT_FOR_KERNEL_MOUNT, ns->user_ns);

Or you could just change fc->user_ns immediately after calling
vfs_new_fs_context().  This is what network filesystems should do with
fc->net_ns, for example.

> -struct fs_context *vfs_new_fs_context(struct file_system_type *fs_type,
> +struct fs_context *vfs_new_fs_context_userns(struct file_system_type *fs_type,
>  				      struct dentry *reference,
>  				      unsigned int sb_flags,
> -				      enum fs_context_purpose purpose)
> +				      enum fs_context_purpose purpose,
> +				      struct user_namespace *user_ns)


If you'd really rather add a new parameter, please don't rename the function
to vfs_new_fs_context_userns() - just add a new parameter.  There don't need
to be two versions of it.


This brings me to another thought:  I want to add the ability to let
namespaces be configured by userspace, for example:

	fd = fsopen("nfs");
	sprintf(buf, "ns user %d", my_user_ns_fd);
	write(fd, buf);
	sprintf(buf, "ns net %d", my_net_ns_fd);
	write(fd, buf);
	write(fd, "s fedoraproject.org:/pub");
	write(fd, "o intr");
	...

I think therefore, I might need to insert another phase between creating the
context and calling the filesystem initialiser:

	fc = vfs_new_fs_context(&afs_fs_type, mntpt, 0,
				FS_CONTEXT_FOR_SUBMOUNT);

followed by:

	vfs_sb_set_namespace(fc, THIS_IS_USER_NS, user_ns);
	vfs_sb_set_namespace(fc, THIS_IS_NET_NS, net_ns);

but then we'd need to do:

	vfs_begin_options(fc);

before continuing (unless we made this happen automatically on the receipt of
the first option):

	afs_mntpt_set_params(fc, mntpt);
	vfs_get_tree(fc);
	mnt = vfs_create_mount(fc, 0);

Alternatively, we could do the namespace setting after initialisation and let
the fs apply the changes itself.

David

  parent reply	other threads:[~2018-06-26  8:57 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-19 13:31 [PATCH 00/24] VFS: Introduce filesystem context " David Howells
2018-04-19 13:31 ` [PATCH 01/24] vfs: Undo an overly zealous MS_RDONLY -> SB_RDONLY conversion " David Howells
2018-04-19 13:31 ` [PATCH 02/24] VFS: Suppress MS_* flag defs within the kernel unless explicitly enabled " David Howells
2018-04-19 13:31 ` [PATCH 03/24] VFS: Introduce the structs and doc for a filesystem context " David Howells
2018-04-23  3:36   ` Randy Dunlap
2018-05-01 14:29   ` David Howells
2018-05-01 15:31     ` Randy Dunlap
2018-04-19 13:31 ` [PATCH 04/24] VFS: Add LSM hooks for " David Howells
2018-04-19 20:32   ` Paul Moore
2018-04-20 15:35   ` David Howells
2018-04-23 13:25     ` Stephen Smalley
2018-04-24 15:22     ` David Howells
2018-04-25 14:07       ` Stephen Smalley
2018-04-19 13:31 ` [PATCH 05/24] apparmor: Implement security hooks for the new mount API " David Howells
2018-05-04  0:10   ` John Johansen
2018-05-11 12:20   ` David Howells
2018-04-19 13:31 ` [PATCH 06/24] tomoyo: " David Howells
2018-04-19 13:31 ` [PATCH 07/24] smack: Implement filesystem context security hooks " David Howells
2018-04-19 13:31 ` [PATCH 08/24] VFS: Require specification of size of mount data for internal mounts " David Howells
2018-04-19 13:32 ` [PATCH 09/24] VFS: Implement a filesystem superblock creation/configuration context " David Howells
2018-04-19 13:32 ` [PATCH 10/24] VFS: Remove unused code after filesystem context changes " David Howells
2018-04-19 13:32 ` [PATCH 11/24] procfs: Move proc_fill_super() to fs/proc/root.c " David Howells
2018-04-19 13:32 ` [PATCH 12/24] proc: Add fs_context support to procfs " David Howells
2018-06-19  3:34   ` [12/24] " Andrei Vagin
2018-06-26  6:13     ` Andrei Vagin
2018-06-26  7:27       ` Andrei Vagin
2018-06-26  8:57       ` David Howells [this message]
2018-06-28  5:50         ` Andrei Vagin
2018-04-19 13:32 ` [PATCH 13/24] ipc: Convert mqueue fs to fs_context " David Howells
2018-04-19 13:32 ` [PATCH 14/24] cpuset: Use " David Howells
2018-04-19 13:32 ` [PATCH 15/24] kernfs, sysfs, cgroup, intel_rdt: Support " David Howells
2018-04-19 13:33 ` [PATCH 16/24] hugetlbfs: Convert to " David Howells
2018-04-19 13:33 ` [PATCH 17/24] VFS: Remove kern_mount_data() " David Howells
2018-04-19 13:33 ` [PATCH 18/24] VFS: Implement fsopen() to prepare for a mount " David Howells
2018-04-19 13:33 ` [PATCH 19/24] VFS: Implement fsmount() to effect a pre-configured " David Howells
2018-04-19 13:33 ` [PATCH 20/24] afs: Fix server record deletion " David Howells
2018-04-19 13:33 ` [PATCH 21/24] net: Export get_proc_net() " David Howells
2018-04-19 13:33 ` [PATCH 22/24] afs: Add fs_context support " David Howells
2018-04-19 13:33 ` [PATCH 23/24] afs: Implement namespacing " David Howells
2018-04-19 13:33 ` [PATCH 24/24] afs: Use fs_context to pass parameters over automount " David Howells

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