From: ebiederm@xmission.com (Eric W. Biederman)
To: David Howells <dhowells@redhat.com>
Cc: keyrings@vger.kernel.org, trond.myklebust@hammerspace.com,
sfrench@samba.org, linux-security-module@vger.kernel.org,
linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org,
linux-fsdevel@vger.kernel.org, rgb@redhat.com,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 06/27] containers, vfs: Allow syscall dirfd arguments to take a container fd
Date: Tue, 19 Feb 2019 10:45:33 -0600 [thread overview]
Message-ID: <8736ojwwuq.fsf@xmission.com> (raw)
In-Reply-To: <155024688620.21651.16013251077091180213.stgit@warthog.procyon.org.uk> (David Howells's message of "Fri, 15 Feb 2019 16:08:06 +0000")
David Howells <dhowells@redhat.com> writes:
> Some filesystem system calls, such as mkdirat(), take a 'directory fd' to
> specify the pathwalk origin. This takes either AT_FDCWD or a file
> descriptor that refers to an open directory.
>
> Make it possible to supply a container fd, as obtained from
> container_create(), instead thereby specifying the container's root as the
> origin. This performs the filesystem operation into the container's mount
> namespace. For example:
>
> int cfd = container_create("fred", CONTAINER_NEW_MNT_NS, 0);
> mkdirat(cfd, "/fred", 0755);
>
> A better way to do this might be to temporarily override current->fs and
> current->nsproxy, but this requires splitting those fields so that procfs
> doesn't see the override.
>
> A sequence number and lock are available to protect the root pointer in
> case container_chroot() and/or container_pivot_root() are implemented.
If this is desirable we can do this without a ``container''. We already
have mount namespaces.
Nacked-by: "Eric W. Biederman" <ebiederm@xmission.com>
In fact if you take care to use a path that starts with '/' the normal
dirfd based operations work just fine.
So I don't see the point of this system call at all.
> Signed-off-by: David Howells <dhowells@redhat.com>
> ---
>
> fs/namei.c | 45 ++++++++++++++++++++++++++++++++++-----------
> 1 file changed, 34 insertions(+), 11 deletions(-)
>
> diff --git a/fs/namei.c b/fs/namei.c
> index a85deb55d0c9..4932b5467285 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -2232,20 +2232,43 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
> if (!f.file)
> return ERR_PTR(-EBADF);
>
> - dentry = f.file->f_path.dentry;
> + if (is_container_file(f.file)) {
> + struct container *c = f.file->private_data;
> + unsigned seq;
>
> - if (*s && unlikely(!d_can_lookup(dentry))) {
> - fdput(f);
> - return ERR_PTR(-ENOTDIR);
> - }
> + if (!*s)
> + return ERR_PTR(-EINVAL);
>
> - nd->path = f.file->f_path;
> - if (flags & LOOKUP_RCU) {
> - nd->inode = nd->path.dentry->d_inode;
> - nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
> + if (flags & LOOKUP_RCU) {
> + do {
> + seq = read_seqcount_begin(&c->seq);
> + nd->path = c->root;
> + nd->inode = nd->path.dentry->d_inode;
> + nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
> + } while (read_seqcount_retry(&c->seq, seq));
> + } else {
> + spin_lock(&c->lock);
> + nd->path = c->root;
> + path_get(&nd->path);
> + spin_unlock(&c->lock);
> + nd->inode = nd->path.dentry->d_inode;
> + }
> } else {
> - path_get(&nd->path);
> - nd->inode = nd->path.dentry->d_inode;
> + dentry = f.file->f_path.dentry;
> +
> + if (*s && unlikely(!d_can_lookup(dentry))) {
> + fdput(f);
> + return ERR_PTR(-ENOTDIR);
> + }
> +
> + nd->path = f.file->f_path;
> + if (flags & LOOKUP_RCU) {
> + nd->inode = nd->path.dentry->d_inode;
> + nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
> + } else {
> + path_get(&nd->path);
> + nd->inode = nd->path.dentry->d_inode;
> + }
> }
> fdput(f);
> return s;
next prev parent reply other threads:[~2019-02-19 16:45 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-15 16:07 [RFC PATCH 00/27] Containers and using authenticated filesystems David Howells
2019-02-15 16:07 ` [RFC PATCH 01/27] containers: Rename linux/container.h to linux/container_dev.h David Howells
2019-02-15 16:07 ` [RFC PATCH 02/27] containers: Implement containers as kernel objects David Howells
2019-02-17 18:57 ` Trond Myklebust
2019-02-17 19:39 ` James Bottomley
2019-02-19 16:56 ` Eric W. Biederman
2019-02-19 23:03 ` David Howells
2019-02-20 14:23 ` Trond Myklebust
2019-02-19 23:06 ` David Howells
2019-02-20 2:20 ` James Bottomley
2019-02-20 3:04 ` Ian Kent
2019-02-20 3:46 ` James Bottomley
2019-02-20 4:42 ` Ian Kent
2019-02-20 6:57 ` Paul Moore
2019-02-19 23:13 ` David Howells
2019-02-19 23:55 ` Tycho Andersen
2019-02-20 2:46 ` Ian Kent
2019-02-20 13:26 ` Christian Brauner
2019-02-21 10:39 ` Ian Kent
2019-02-15 16:07 ` [RFC PATCH 03/27] containers: Provide /proc/containers David Howells
2019-02-15 16:07 ` [RFC PATCH 04/27] containers: Allow a process to be forked into a container David Howells
2019-02-15 17:39 ` Stephen Smalley
2019-02-19 16:39 ` Eric W. Biederman
2019-02-19 23:16 ` David Howells
2019-02-15 16:07 ` [RFC PATCH 05/27] containers: Open a socket inside " David Howells
2019-02-19 16:41 ` Eric W. Biederman
2019-02-15 16:08 ` [RFC PATCH 06/27] containers, vfs: Allow syscall dirfd arguments to take a container fd David Howells
2019-02-19 16:45 ` Eric W. Biederman [this message]
2019-02-19 23:24 ` David Howells
2019-02-15 16:08 ` [RFC PATCH 07/27] containers: Make fsopen() able to create a superblock in a container David Howells
2019-02-15 16:08 ` [RFC PATCH 08/27] containers, vfs: Honour CONTAINER_NEW_EMPTY_FS_NS David Howells
2019-02-17 0:11 ` Al Viro
2019-02-15 16:08 ` [RFC PATCH 09/27] vfs: Allow mounting to other namespaces David Howells
2019-02-17 0:14 ` Al Viro
2019-02-15 16:08 ` [RFC PATCH 10/27] containers: Provide fs_context op for container setting David Howells
2019-02-15 16:09 ` [RFC PATCH 11/27] containers: Sample program for driving container objects David Howells
2019-02-15 16:09 ` [RFC PATCH 12/27] containers: Allow a daemon to intercept request_key upcalls in a container David Howells
2019-02-15 16:09 ` [RFC PATCH 13/27] keys: Provide a keyctl to query a request_key authentication key David Howells
2019-02-15 16:09 ` [RFC PATCH 14/27] keys: Break bits out of key_unlink() David Howells
2019-02-15 16:09 ` [RFC PATCH 15/27] keys: Make __key_link_begin() handle lockdep nesting David Howells
2019-02-15 16:09 ` [RFC PATCH 16/27] keys: Grant Link permission to possessers of request_key auth keys David Howells
2019-02-15 16:10 ` [RFC PATCH 17/27] keys: Add a keyctl to move a key between keyrings David Howells
2019-02-15 16:10 ` [RFC PATCH 18/27] keys: Find the least-recently used unseen key in a keyring David Howells
2019-02-15 16:10 ` [RFC PATCH 19/27] containers: Sample: request_key upcall handling David Howells
2019-02-15 16:10 ` [RFC PATCH 20/27] container, keys: Add a container keyring David Howells
2019-02-15 21:46 ` Eric Biggers
2019-02-15 16:11 ` [RFC PATCH 21/27] keys: Fix request_key() lack of Link perm check on found key David Howells
2019-02-15 16:11 ` [RFC PATCH 22/27] KEYS: Replace uid/gid/perm permissions checking with an ACL David Howells
2019-02-15 17:32 ` Stephen Smalley
2019-02-15 17:39 ` David Howells
2019-02-15 16:11 ` [RFC PATCH 23/27] KEYS: Provide KEYCTL_GRANT_PERMISSION David Howells
2019-02-15 16:11 ` [RFC PATCH 24/27] keys: Allow a container to be specified as a subject in a key's ACL David Howells
2019-02-15 16:11 ` [RFC PATCH 25/27] keys: Provide a way to ask for the container keyring David Howells
2019-02-15 16:12 ` [RFC PATCH 26/27] keys: Allow containers to be included in key ACLs by name David Howells
2019-02-15 16:12 ` [RFC PATCH 27/27] containers: Sample to grant access to a key in a container David Howells
2019-02-15 22:36 ` [RFC PATCH 00/27] Containers and using authenticated filesystems James Morris
2019-02-19 16:35 ` Eric W. Biederman
2019-02-20 14:18 ` Christian Brauner
2019-02-19 23:42 ` David Howells
2019-02-20 7:00 ` Paul Moore
2019-02-20 18:54 ` Steve French
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