linux-toradex.git/include/linux/mount.h, branch v6.4-rc1

Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2023-02-25T03:20:07+00:00

Pull ipc namespace update from Al Viro:
 "Rik's patches reducing the amount of synchronize_rcu() triggered by
  ipc namespace destruction.

  I've some pending stuff reducing that on the normal umount side, but
  it's nowhere near ready and Rik's stuff shouldn't be held back due to
  conflicts - I'll just redo the parts of my series that stray into
  ipc/*"

* 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  ipc,namespace: batch free ipc_namespace structures
  ipc,namespace: make ipc namespace allocation wait for pending free

ipc,namespace: batch free ipc_namespace structures

2023-01-28T00:08:00+00:00

Instead of waiting for an RCU grace period between each ipc_namespace
structure that is being freed, wait an RCU grace period for every batch
of ipc_namespace structures.

Thanks to Al Viro for the suggestion of the helper function.

This speeds up the run time of the test case that allocates ipc_namespaces
in a loop from 6 minutes, to a little over 1 second:

real	0m1.192s
user	0m0.038s
sys	0m1.152s

Signed-off-by: Rik van Riel 
Reported-by: Chris Mason 
Tested-by: Giuseppe Scrivano 
Suggested-by: Al Viro 
Signed-off-by: Al Viro

fs: move mnt_idmap

2023-01-19T08:24:30+00:00

Now that we converted everything to just rely on struct mnt_idmap move it all
into a separate file. This ensure that no code can poke around in struct
mnt_idmap without any dedicated helpers and makes it easier to extend it in the
future. Filesystems will now not be able to conflate mount and filesystem
idmappings as they are two distinct types and require distinct helpers that
cannot be used interchangeably. We are now also able to extend struct mnt_idmap
as we see fit.

Acked-by: Dave Chinner 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Christian Brauner (Microsoft)

fs: port i_{g,u}id_into_vfs{g,u}id() to mnt_idmap

2023-01-19T08:24:29+00:00

Convert to struct mnt_idmap.
Remove legacy file_mnt_user_ns() and mnt_user_ns().

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.

Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Christian Brauner (Microsoft)

fs: introduce dedicated idmap type for mounts

2022-10-31T16:47:42+00:00

Last cycle we've already made the interaction with idmapped mounts more
robust and type safe by introducing the vfs{g,u}id_t type. This cycle we
concluded the conversion and removed the legacy helpers.

Currently we still pass around the plain namespace that was attached to
a mount. This is in general pretty convenient but it makes it easy to
conflate filesystem and mount namespaces and what different roles they
have to play. Especially for filesystem developers without much
experience in this area this is an easy source for bugs.

Instead of passing the plain namespace we introduce a dedicated type
struct mnt_idmap and replace the pointer with a pointer to a struct
mnt_idmap. There are no semantic or size changes for the mount struct
caused by this.

We then start converting all places aware of idmapped mounts to rely on
struct mnt_idmap. Once the conversion is done all helpers down to the
really low-level make_vfs{g,u}id() and from_vfs{g,u}id() will take a
struct mnt_idmap argument instead of two namespace arguments. This way
it becomes impossible to conflate the two, removing and thus eliminating
the possibility of any bugs. Fwiw, I fixed some issues in that area a
while ago in ntfs3 and ksmbd in the past. Afterwards, only low-level
code can ultimately use the associated namespace for any permission
checks. Even most of the vfs can be ultimately completely oblivious
about this and filesystems will never interact with it directly in any
form in the future.

A struct mnt_idmap currently encompasses a simple refcount and a pointer
to the relevant namespace the mount is idmapped to. If a mount isn't
idmapped then it will point to a static nop_mnt_idmap. If it is an
idmapped mount it will point to a new struct mnt_idmap. As usual there
are no allocations or anything happening for non-idmapped mounts.
Everthing is carefully written to be a nop for non-idmapped mounts as
has always been the case.

If an idmapped mount or mount tree is created a new struct mnt_idmap is
allocated and a reference taken on the relevant namespace. For each
mount in a mount tree that gets idmapped or a mount that inherits the
idmap when it is cloned the reference count on the associated struct
mnt_idmap is bumped. Just a reminder that we only allow a mount to
change it's idmapping a single time and only if it hasn't already been
attached to the filesystems and has no active writers.

The actual changes are fairly straightforward. This will have huge
benefits for maintenance and security in the long run even if it causes
some churn. I'm aware that there's some cost for all of you. And I'll
commit to doing this work and make this as painless as I can.

Note that this also makes it possible to extend struct mount_idmap in
the future. For example, it would be possible to place the namespace
pointer in an anonymous union together with an idmapping struct. This
would allow us to expose an api to userspace that would let it specify
idmappings directly instead of having to go through the detour of
setting up namespaces at all.

This just adds the infrastructure and doesn't do any conversions.

Reviewed-by: Seth Forshee (DigitalOcean) 
Signed-off-by: Christian Brauner (Microsoft)

move mount-related externs from fs.h to mount.h

2022-05-20T03:25:48+00:00

Signed-off-by: Al Viro

linux/mount.h: trim includes

2022-05-20T03:25:18+00:00

Signed-off-by: Al Viro

fs: move namespace sysctls and declare fs base directory

2022-01-22T06:33:36+00:00

This moves the namespace sysctls to its own file as part of the
kernel/sysctl.c spring cleaning

Since we have now removed all sysctls for "fs", we now have to declare
it on the filesystem code, we do that using the new helper, which
reduces boiler plate code.

We rename init_fs_shared_sysctls() to init_fs_sysctls() to reflect that
now fs/sysctls.c is taking on the burden of being the first to register
the base directory as well.

Lastly, since init code will load in the order in which we link it we
have to move the sysctl code to be linked in early, so that its early
init routine runs prior to other fs code.  This way, other filesystem
code can register their own sysctls using the helpers after this:

  * register_sysctl_init()
  * register_sysctl()

Link: https://lkml.kernel.org/r/20211129211943.640266-3-mcgrof@kernel.org
Signed-off-by: Luis Chamberlain 
Cc: Al Viro 
Cc: Anil S Keshavamurthy 
Cc: Antti Palosaari 
Cc: Christian Brauner 
Cc: "David S. Miller" 
Cc: Eric Biederman 
Cc: Eric Biggers 
Cc: Iurii Zaikin 
Cc: Kees Cook 
Cc: Lukas Middendorf 
Cc: Masami Hiramatsu 
Cc: "Naveen N. Rao" 
Cc: Stephen Kitt 
Cc: Xiaoming Ni 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2021-02-27T16:07:12+00:00

Pull misc vfs updates from Al Viro:
 "Assorted stuff pile - no common topic here"

* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  whack-a-mole: don't open-code iminor/imajor
  9p: fix misuse of sscanf() in v9fs_stat2inode()
  audit_alloc_mark(): don't open-code ERR_CAST()
  fs/inode.c: make inode_init_always() initialize i_ino to 0
  vfs: don't unnecessarily clone write access for writable fds

fs: introduce MOUNT_ATTR_IDMAP

2021-01-24T13:43:45+00:00

Introduce a new mount bind mount property to allow idmapping mounts. The
MOUNT_ATTR_IDMAP flag can be set via the new mount_setattr() syscall
together with a file descriptor referring to a user namespace.

The user namespace referenced by the namespace file descriptor will be
attached to the bind mount. All interactions with the filesystem going
through that mount will be mapped according to the mapping specified in
the user namespace attached to it.

Using user namespaces to mark mounts means we can reuse all the existing
infrastructure in the kernel that already exists to handle idmappings
and can also use this for permission checking to allow unprivileged user
to create idmapped mounts in the future.

Idmapping a mount is decoupled from the caller's user and mount
namespace. This means idmapped mounts can be created in the initial
user namespace which is an important use-case for systemd-homed,
portable usb-sticks between systems, sharing data between the initial
user namespace and unprivileged containers, and other use-cases that
have been brought up. For example, assume a home directory where all
files are owned by uid and gid 1000 and the home directory is brought to
a new laptop where the user has id 12345. The system administrator can
simply create a mount of this home directory with a mapping of
1000:12345:1 and other mappings to indicate the ids should be kept.
(With this it is e.g. also possible to create idmapped mounts on the
host with an identity mapping 1:1:100000 where the root user is not
mapped. A user with root access that e.g. has been pivot rooted into
such a mount on the host will be not be able to execute, read, write, or
create files as root.)

Given that mapping a mount is decoupled from the caller's user namespace
a sufficiently privileged process such as a container manager can set up
an idmapped mount for the container and the container can simply pivot
root to it. There's no need for the container to do anything. The mount
will appear correctly mapped independent of the user namespace the
container uses. This means we don't need to mark a mount as idmappable.

In order to create an idmapped mount the caller must currently be
privileged in the user namespace of the superblock the mount belongs to.
Once a mount has been idmapped we don't allow it to change its mapping.
This keeps permission checking and life-cycle management simple. Users
wanting to change the idmapped can always create a new detached mount
with a different idmapping.

Link: https://lore.kernel.org/r/20210121131959.646623-36-christian.brauner@ubuntu.com
Cc: Christoph Hellwig 
Cc: David Howells 
Cc: Mauricio Vásquez Bernal 
Cc: Al Viro 
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig 
Signed-off-by: Christian Brauner