linux-stable/fs/reiserfs
Linus Torvalds 7d6beb71da idmapped-mounts-v5.12
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Merge tag 'idmapped-mounts-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

Pull idmapped mounts from Christian Brauner:
 "This introduces idmapped mounts which has been in the making for some
  time. Simply put, different mounts can expose the same file or
  directory with different ownership. This initial implementation comes
  with ports for fat, ext4 and with Christoph's port for xfs with more
  filesystems being actively worked on by independent people and
  maintainers.

  Idmapping mounts handle a wide range of long standing use-cases. Here
  are just a few:

   - Idmapped mounts make it possible to easily share files between
     multiple users or multiple machines especially in complex
     scenarios. For example, idmapped mounts will be used in the
     implementation of portable home directories in
     systemd-homed.service(8) where they allow users to move their home
     directory to an external storage device and use it on multiple
     computers where they are assigned different uids and gids. This
     effectively makes it possible to assign random uids and gids at
     login time.

   - It is possible to share files from the host with unprivileged
     containers without having to change ownership permanently through
     chown(2).

   - It is possible to idmap a container's rootfs and without having to
     mangle every file. For example, Chromebooks use it to share the
     user's Download folder with their unprivileged containers in their
     Linux subsystem.

   - It is possible to share files between containers with
     non-overlapping idmappings.

   - Filesystem that lack a proper concept of ownership such as fat can
     use idmapped mounts to implement discretionary access (DAC)
     permission checking.

   - They allow users to efficiently changing ownership on a per-mount
     basis without having to (recursively) chown(2) all files. In
     contrast to chown (2) changing ownership of large sets of files is
     instantenous with idmapped mounts. This is especially useful when
     ownership of a whole root filesystem of a virtual machine or
     container is changed. With idmapped mounts a single syscall
     mount_setattr syscall will be sufficient to change the ownership of
     all files.

   - Idmapped mounts always take the current ownership into account as
     idmappings specify what a given uid or gid is supposed to be mapped
     to. This contrasts with the chown(2) syscall which cannot by itself
     take the current ownership of the files it changes into account. It
     simply changes the ownership to the specified uid and gid. This is
     especially problematic when recursively chown(2)ing a large set of
     files which is commong with the aforementioned portable home
     directory and container and vm scenario.

   - Idmapped mounts allow to change ownership locally, restricting it
     to specific mounts, and temporarily as the ownership changes only
     apply as long as the mount exists.

  Several userspace projects have either already put up patches and
  pull-requests for this feature or will do so should you decide to pull
  this:

   - systemd: In a wide variety of scenarios but especially right away
     in their implementation of portable home directories.

         https://systemd.io/HOME_DIRECTORY/

   - container runtimes: containerd, runC, LXD:To share data between
     host and unprivileged containers, unprivileged and privileged
     containers, etc. The pull request for idmapped mounts support in
     containerd, the default Kubernetes runtime is already up for quite
     a while now: https://github.com/containerd/containerd/pull/4734

   - The virtio-fs developers and several users have expressed interest
     in using this feature with virtual machines once virtio-fs is
     ported.

   - ChromeOS: Sharing host-directories with unprivileged containers.

  I've tightly synced with all those projects and all of those listed
  here have also expressed their need/desire for this feature on the
  mailing list. For more info on how people use this there's a bunch of
  talks about this too. Here's just two recent ones:

      https://www.cncf.io/wp-content/uploads/2020/12/Rootless-Containers-in-Gitpod.pdf
      https://fosdem.org/2021/schedule/event/containers_idmap/

  This comes with an extensive xfstests suite covering both ext4 and
  xfs:

      https://git.kernel.org/brauner/xfstests-dev/h/idmapped_mounts

  It covers truncation, creation, opening, xattrs, vfscaps, setid
  execution, setgid inheritance and more both with idmapped and
  non-idmapped mounts. It already helped to discover an unrelated xfs
  setgid inheritance bug which has since been fixed in mainline. It will
  be sent for inclusion with the xfstests project should you decide to
  merge this.

  In order to support per-mount idmappings vfsmounts are marked with
  user namespaces. The idmapping of the user namespace will be used to
  map the ids of vfs objects when they are accessed through that mount.
  By default all vfsmounts are marked with the initial user namespace.
  The initial user namespace is used to indicate that a mount is not
  idmapped. All operations behave as before and this is verified in the
  testsuite.

  Based on prior discussions we want to attach the whole user namespace
  and not just a dedicated idmapping struct. This allows us to reuse all
  the helpers that already exist for dealing with idmappings instead of
  introducing a whole new range of helpers. In addition, if we decide in
  the future that we are confident enough to enable unprivileged users
  to setup idmapped mounts the permission checking can take into account
  whether the caller is privileged in the user namespace the mount is
  currently marked with.

  The user namespace the mount will be marked with can be specified by
  passing a file descriptor refering to the user namespace as an
  argument to the new mount_setattr() syscall together with the new
  MOUNT_ATTR_IDMAP flag. The system call follows the openat2() pattern
  of extensibility.

  The following conditions must be met in order to create an idmapped
  mount:

   - The caller must currently have the CAP_SYS_ADMIN capability in the
     user namespace the underlying filesystem has been mounted in.

   - The underlying filesystem must support idmapped mounts.

   - The mount must not already be idmapped. This also implies that the
     idmapping of a mount cannot be altered once it has been idmapped.

   - The mount must be a detached/anonymous mount, i.e. it must have
     been created by calling open_tree() with the OPEN_TREE_CLONE flag
     and it must not already have been visible in the filesystem.

  The last two points guarantee easier semantics for userspace and the
  kernel and make the implementation significantly simpler.

  By default vfsmounts are marked with the initial user namespace and no
  behavioral or performance changes are observed.

  The manpage with a detailed description can be found here:

      1d7b902e28

  In order to support idmapped mounts, filesystems need to be changed
  and mark themselves with the FS_ALLOW_IDMAP flag in fs_flags. The
  patches to convert individual filesystem are not very large or
  complicated overall as can be seen from the included fat, ext4, and
  xfs ports. Patches for other filesystems are actively worked on and
  will be sent out separately. The xfstestsuite can be used to verify
  that port has been done correctly.

  The mount_setattr() syscall is motivated independent of the idmapped
  mounts patches and it's been around since July 2019. One of the most
  valuable features of the new mount api is the ability to perform
  mounts based on file descriptors only.

  Together with the lookup restrictions available in the openat2()
  RESOLVE_* flag namespace which we added in v5.6 this is the first time
  we are close to hardened and race-free (e.g. symlinks) mounting and
  path resolution.

  While userspace has started porting to the new mount api to mount
  proper filesystems and create new bind-mounts it is currently not
  possible to change mount options of an already existing bind mount in
  the new mount api since the mount_setattr() syscall is missing.

  With the addition of the mount_setattr() syscall we remove this last
  restriction and userspace can now fully port to the new mount api,
  covering every use-case the old mount api could. We also add the
  crucial ability to recursively change mount options for a whole mount
  tree, both removing and adding mount options at the same time. This
  syscall has been requested multiple times by various people and
  projects.

  There is a simple tool available at

      https://github.com/brauner/mount-idmapped

  that allows to create idmapped mounts so people can play with this
  patch series. I'll add support for the regular mount binary should you
  decide to pull this in the following weeks:

  Here's an example to a simple idmapped mount of another user's home
  directory:

	u1001@f2-vm:/$ sudo ./mount --idmap both:1000:1001:1 /home/ubuntu/ /mnt

	u1001@f2-vm:/$ ls -al /home/ubuntu/
	total 28
	drwxr-xr-x 2 ubuntu ubuntu 4096 Oct 28 22:07 .
	drwxr-xr-x 4 root   root   4096 Oct 28 04:00 ..
	-rw------- 1 ubuntu ubuntu 3154 Oct 28 22:12 .bash_history
	-rw-r--r-- 1 ubuntu ubuntu  220 Feb 25  2020 .bash_logout
	-rw-r--r-- 1 ubuntu ubuntu 3771 Feb 25  2020 .bashrc
	-rw-r--r-- 1 ubuntu ubuntu  807 Feb 25  2020 .profile
	-rw-r--r-- 1 ubuntu ubuntu    0 Oct 16 16:11 .sudo_as_admin_successful
	-rw------- 1 ubuntu ubuntu 1144 Oct 28 00:43 .viminfo

	u1001@f2-vm:/$ ls -al /mnt/
	total 28
	drwxr-xr-x  2 u1001 u1001 4096 Oct 28 22:07 .
	drwxr-xr-x 29 root  root  4096 Oct 28 22:01 ..
	-rw-------  1 u1001 u1001 3154 Oct 28 22:12 .bash_history
	-rw-r--r--  1 u1001 u1001  220 Feb 25  2020 .bash_logout
	-rw-r--r--  1 u1001 u1001 3771 Feb 25  2020 .bashrc
	-rw-r--r--  1 u1001 u1001  807 Feb 25  2020 .profile
	-rw-r--r--  1 u1001 u1001    0 Oct 16 16:11 .sudo_as_admin_successful
	-rw-------  1 u1001 u1001 1144 Oct 28 00:43 .viminfo

	u1001@f2-vm:/$ touch /mnt/my-file

	u1001@f2-vm:/$ setfacl -m u:1001:rwx /mnt/my-file

	u1001@f2-vm:/$ sudo setcap -n 1001 cap_net_raw+ep /mnt/my-file

	u1001@f2-vm:/$ ls -al /mnt/my-file
	-rw-rwxr--+ 1 u1001 u1001 0 Oct 28 22:14 /mnt/my-file

	u1001@f2-vm:/$ ls -al /home/ubuntu/my-file
	-rw-rwxr--+ 1 ubuntu ubuntu 0 Oct 28 22:14 /home/ubuntu/my-file

	u1001@f2-vm:/$ getfacl /mnt/my-file
	getfacl: Removing leading '/' from absolute path names
	# file: mnt/my-file
	# owner: u1001
	# group: u1001
	user::rw-
	user:u1001:rwx
	group::rw-
	mask::rwx
	other::r--

	u1001@f2-vm:/$ getfacl /home/ubuntu/my-file
	getfacl: Removing leading '/' from absolute path names
	# file: home/ubuntu/my-file
	# owner: ubuntu
	# group: ubuntu
	user::rw-
	user:ubuntu:rwx
	group::rw-
	mask::rwx
	other::r--"

* tag 'idmapped-mounts-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: (41 commits)
  xfs: remove the possibly unused mp variable in xfs_file_compat_ioctl
  xfs: support idmapped mounts
  ext4: support idmapped mounts
  fat: handle idmapped mounts
  tests: add mount_setattr() selftests
  fs: introduce MOUNT_ATTR_IDMAP
  fs: add mount_setattr()
  fs: add attr_flags_to_mnt_flags helper
  fs: split out functions to hold writers
  namespace: only take read lock in do_reconfigure_mnt()
  mount: make {lock,unlock}_mount_hash() static
  namespace: take lock_mount_hash() directly when changing flags
  nfs: do not export idmapped mounts
  overlayfs: do not mount on top of idmapped mounts
  ecryptfs: do not mount on top of idmapped mounts
  ima: handle idmapped mounts
  apparmor: handle idmapped mounts
  fs: make helpers idmap mount aware
  exec: handle idmapped mounts
  would_dump: handle idmapped mounts
  ...
2021-02-23 13:39:45 -08:00
..
acl.h fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
bitmap.c treewide: Use array_size() in vmalloc() 2018-06-12 16:19:22 -07:00
dir.c reiserfs: delete duplicated words 2020-08-05 10:29:57 +02:00
do_balan.c reiserfs: clean up several indentation issues 2020-04-07 10:43:44 -07:00
file.c block: use an on-stack bio in blkdev_issue_flush 2021-01-27 09:51:48 -07:00
fix_node.c reiserfs: delete duplicated words 2020-08-05 10:29:57 +02:00
hashes.c reiserfs: cleanup, reformat comments to normal kernel style 2014-05-06 22:52:19 +02:00
ibalance.c reiserfs: fix "new_insert_key may be used uninitialized ..." 2016-08-02 19:35:22 -04:00
inode.c fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
ioctl.c inode: make init and permission helpers idmapped mount aware 2021-01-24 14:27:16 +01:00
item_ops.c reiserfs: remove obsolete print_time function 2018-08-22 10:52:50 -07:00
journal.c reiserfs: delete duplicated words 2020-08-05 10:29:57 +02:00
Kconfig treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
lbalance.c fs/reiserfs/lbalance.c: remove set but not used variables 2019-09-25 17:51:40 -07:00
lock.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Makefile reiserfs: remove workaround code for GCC 3.x 2018-10-31 08:54:14 -07:00
namei.c fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
objectid.c fs/reiserfs/objectid.c: remove set but not used variables 2019-09-25 17:51:40 -07:00
prints.c fs/reiserfs/prints.c: remove set but not used variables 2019-09-25 17:51:40 -07:00
procfs.c block: move block-related definitions out of fs.h 2020-06-24 09:16:02 -06:00
README
reiserfs.h fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
resize.c treewide: Use array_size() in vzalloc() 2018-06-12 16:19:22 -07:00
stree.c reiserfs: add check for an invalid ih_entry_count 2020-11-26 16:57:28 +01:00
super.c reiserfs: Fix memory leak in reiserfs_parse_options() 2020-08-28 17:11:53 +02:00
tail_conversion.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
xattr.c fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
xattr.h fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
xattr_acl.c fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
xattr_security.c acl: handle idmapped mounts 2021-01-24 14:27:17 +01:00
xattr_trusted.c acl: handle idmapped mounts 2021-01-24 14:27:17 +01:00
xattr_user.c acl: handle idmapped mounts 2021-01-24 14:27:17 +01:00

[LICENSING]

ReiserFS is hereby licensed under the GNU General
Public License version 2.

Source code files that contain the phrase "licensing governed by
reiserfs/README" are "governed files" throughout this file.  Governed
files are licensed under the GPL.  The portions of them owned by Hans
Reiser, or authorized to be licensed by him, have been in the past,
and likely will be in the future, licensed to other parties under
other licenses.  If you add your code to governed files, and don't
want it to be owned by Hans Reiser, put your copyright label on that
code so the poor blight and his customers can keep things straight.
All portions of governed files not labeled otherwise are owned by Hans
Reiser, and by adding your code to it, widely distributing it to
others or sending us a patch, and leaving the sentence in stating that
licensing is governed by the statement in this file, you accept this.
It will be a kindness if you identify whether Hans Reiser is allowed
to license code labeled as owned by you on your behalf other than
under the GPL, because he wants to know if it is okay to do so and put
a check in the mail to you (for non-trivial improvements) when he
makes his next sale.  He makes no guarantees as to the amount if any,
though he feels motivated to motivate contributors, and you can surely
discuss this with him before or after contributing.  You have the
right to decline to allow him to license your code contribution other
than under the GPL.

Further licensing options are available for commercial and/or other
interests directly from Hans Reiser: hans@reiser.to.  If you interpret
the GPL as not allowing those additional licensing options, you read
it wrongly, and Richard Stallman agrees with me, when carefully read
you can see that those restrictions on additional terms do not apply
to the owner of the copyright, and my interpretation of this shall
govern for this license.

Finally, nothing in this license shall be interpreted to allow you to
fail to fairly credit me, or to remove my credits, without my
permission, unless you are an end user not redistributing to others.
If you have doubts about how to properly do that, or about what is
fair, ask.  (Last I spoke with him Richard was contemplating how best
to address the fair crediting issue in the next GPL version.)

[END LICENSING]

Reiserfs is a file system based on balanced tree algorithms, which is
described at https://reiser4.wiki.kernel.org/index.php/Main_Page 

Stop reading here.  Go there, then return.

Send bug reports to yura@namesys.botik.ru.

mkreiserfs and other utilities are in reiserfs/utils, or wherever your
Linux provider put them.  There is some disagreement about how useful
it is for users to get their fsck and mkreiserfs out of sync with the
version of reiserfs that is in their kernel, with many important
distributors wanting them out of sync.:-) Please try to remember to
recompile and reinstall fsck and mkreiserfs with every update of
reiserfs, this is a common source of confusion.  Note that some of the
utilities cannot be compiled without accessing the balancing code
which is in the kernel code, and relocating the utilities may require
you to specify where that code can be found.

Yes, if you update your reiserfs kernel module you do have to
recompile your kernel, most of the time.  The errors you get will be
quite cryptic if your forget to do so.

Real users, as opposed to folks who want to hack and then understand
what went wrong, will want REISERFS_CHECK off.

Hideous Commercial Pitch: Spread your development costs across other OS
vendors.  Select from the best in the world, not the best in your
building, by buying from third party OS component suppliers.  Leverage
the software component development power of the internet.  Be the most
aggressive in taking advantage of the commercial possibilities of
decentralized internet development, and add value through your branded
integration that you sell as an operating system.  Let your competitors
be the ones to compete against the entire internet by themselves.  Be
hip, get with the new economic trend, before your competitors do.  Send
email to hans@reiser.to.

To understand the code, after reading the website, start reading the
code by reading reiserfs_fs.h first.

Hans Reiser was the project initiator, primary architect, source of all
funding for the first 5.5 years, and one of the programmers.  He owns
the copyright.

Vladimir Saveljev was one of the programmers, and he worked long hours
writing the cleanest code.  He always made the effort to be the best he
could be, and to make his code the best that it could be.  What resulted
was quite remarkable. I don't think that money can ever motivate someone
to work the way he did, he is one of the most selfless men I know.

Yura helps with benchmarking, coding hashes, and block pre-allocation
code.

Anatoly Pinchuk is a former member of our team who worked closely with
Vladimir throughout the project's development.  He wrote a quite
substantial portion of the total code.  He realized that there was a
space problem with packing tails of files for files larger than a node
that start on a node aligned boundary (there are reasons to want to node
align files), and he invented and implemented indirect items and
unformatted nodes as the solution.

Konstantin Shvachko, with the help of the Russian version of a VC,
tried to put me in a position where I was forced into giving control
of the project to him.  (Fortunately, as the person paying the money
for all salaries from my dayjob I owned all copyrights, and you can't
really force takeovers of sole proprietorships.)  This was something
curious, because he never really understood the value of our project,
why we should do what we do, or why innovation was possible in
general, but he was sure that he ought to be controlling it.  Every
innovation had to be forced past him while he was with us.  He added
two years to the time required to complete reiserfs, and was a net
loss for me.  Mikhail Gilula was a brilliant innovator who also left
in a destructive way that erased the value of his contributions, and
that he was shown much generosity just makes it more painful.

Grigory Zaigralin was an extremely effective system administrator for
our group.

Igor Krasheninnikov was wonderful at hardware procurement, repair, and
network installation.

Jeremy Fitzhardinge wrote the teahash.c code, and he gives credit to a
textbook he got the algorithm from in the code.  Note that his analysis
of how we could use the hashing code in making 32 bit NFS cookies work
was probably more important than the actual algorithm.  Colin Plumb also
contributed to it.

Chris Mason dived right into our code, and in just a few months produced
the journaling code that dramatically increased the value of ReiserFS.
He is just an amazing programmer.

Igor Zagorovsky is writing much of the new item handler and extent code
for our next major release.

Alexander Zarochentcev (sometimes known as zam, or sasha), wrote the
resizer, and is hard at work on implementing allocate on flush.  SGI
implemented allocate on flush before us for XFS, and generously took
the time to convince me we should do it also.  They are great people,
and a great company.

Yuri Shevchuk and Nikita Danilov are doing squid cache optimization.

Vitaly Fertman is doing fsck.

Jeff Mahoney, of SuSE, contributed a few cleanup fixes, most notably
the endian safe patches which allow ReiserFS to run on any platform
supported by the Linux kernel.

SuSE, IntegratedLinux.com, Ecila, MP3.com, bigstorage.com, and the
Alpha PC Company made it possible for me to not have a day job
anymore, and to dramatically increase our staffing.  Ecila funded
hypertext feature development, MP3.com funded journaling, SuSE funded
core development, IntegratedLinux.com funded squid web cache
appliances, bigstorage.com funded HSM, and the alpha PC company funded
the alpha port.  Many of these tasks were helped by sponsors other
than the ones just named.  SuSE has helped in much more than just
funding....