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Convert to struct mnt_idmap.
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 <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
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The posix acl permission checking helpers determine whether a caller is
privileged over an inode according to the acls associated with the
inode. Add helpers that make it possible to handle acls on idmapped
mounts.
The vfs and the filesystems targeted by this first iteration make use of
posix_acl_fix_xattr_from_user() and posix_acl_fix_xattr_to_user() to
translate basic posix access and default permissions such as the
ACL_USER and ACL_GROUP type according to the initial user namespace (or
the superblock's user namespace) to and from the caller's current user
namespace. Adapt these two helpers to handle idmapped mounts whereby we
either map from or into the mount's user namespace depending on in which
direction we're translating.
Similarly, cap_convert_nscap() is used by the vfs to translate user
namespace and non-user namespace aware filesystem capabilities from the
superblock's user namespace to the caller's user namespace. Enable it to
handle idmapped mounts by accounting for the mount's user namespace.
In addition the fileystems targeted in the first iteration of this patch
series make use of the posix_acl_chmod() and, posix_acl_update_mode()
helpers. Both helpers perform permission checks on the target inode. Let
them handle idmapped mounts. These two helpers are called when posix
acls are set by the respective filesystems to handle this case we extend
the ->set() method to take an additional user namespace argument to pass
the mount's user namespace down.
Link: https://lore.kernel.org/r/20210121131959.646623-9-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
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The Hurd gained[0] support for moving the translator and author
fields out of the inode and into the "gnu.*" xattr namespace.
In anticipation of that, an xattr INDEX was reserved[1]. The Hurd has
now been brought into compliance[2] with that.
This patch adds support for reading and writing such attributes from
Linux; you can now do something like
mkdir -p hurd-root/servers/socket
touch hurd-root/servers/socket/1
setfattr --name=gnu.translator --value='"/hurd/pflocal\0"' \
hurd-root/servers/socket/1
getfattr --name=gnu.translator hurd-root/servers/socket/1
# file: 1
gnu.translator="/hurd/pflocal"
to setup a pipe translator, which is being used to create[3] a
vm-image for the Hurd from GNU Guix.
[0] https://summerofcode.withgoogle.com/projects/#5869799859027968
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3980bd3b406addb327d858aebd19e229ea340b9a
[2] https://git.savannah.gnu.org/cgit/hurd/hurd.git/commit/?id=a04c7bf83172faa7cb080fbe3b6c04a8415ca645
[3] https://git.savannah.gnu.org/cgit/guix.git/log/?h=wip-hurd-vm
Signed-off-by: Jan Nieuwenhuizen <janneke@gnu.org>
Link: https://lore.kernel.org/r/20200525193940.878-1-janneke@gnu.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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