Hey Linus,
/* Summary */
This contains the work that builds a dedicated vfs posix acl api. The origins
of this work trace back to v5.19 but it took quite a while to understand the
various filesystem specific implementations in sufficient detail and also come
up with an acceptable solution.
As we discussed and seen multiple times the current state of how posix acls are
handled isn't nice and comes with a lot of problems. For a long and detailed
explanation for just some of the issues [1] provides a good summary.
The current way of handling posix acls via the generic xattr api is error
prone, hard to maintain, and type unsafe for the vfs until we call into the
filesystem's dedicated get and set inode operations.
It is already the case that posix acls are special-cased to death all the way
through the vfs. There are an uncounted number of hacks that operate on the
uapi posix acl struct instead of the dedicated vfs struct posix_acl. And the
vfs must be involved in order to interpret and fixup posix acls before storing
them to the backing store, caching them, reporting them to userspace, or for
permission checking.
Currently a range of hacks and duct tape exist to make this work. As with most
things this is really no ones fault it's just something that happened over
time. But the code is hard to understand and difficult to maintain and one is
constantly at risk of introducing bugs and regressions when having to touch it.
Instead of continuing to hack posix acls through the xattr handlers this series
builds a dedicated posix acl api solely around the get and set inode
operations. Going forward, the vfs_get_acl(), vfs_remove_acl(), and
vfs_set_acl() helpers must be used in order to interact with posix acls. They
operate directly on the vfs internal struct posix_acl instead of abusing the
uapi posix acl struct as we currently do. In the end this removes all of the
hackiness, makes the codepaths easier to maintain, and gets us type safety.
This series passes the LTP and xfstests suites without any regressions. For
xfstests the following combinations were tested:
* xfs
* ext4
* btrfs
* overlayfs
* overlayfs on top of idmapped mounts
* orangefs
* (limited) cifs
There's more simplifications for posix acls that we can make in the future if
the basic api has made it.
A few implementation details:
* The series makes sure to retain exactly the same security and integrity module
permission checks. See [2] for annotated callchains. Especially for the
integrity modules this api is a win because right now they convert the uapi
posix acl struct passed to them via a void pointer into the vfs struct
posix_acl format to perform permission checking on the mode.
There's a new dedicated security hook for setting posix acls which passes the
vfs struct posix_acl not a void pointer. Basing checking on the posix acl
stored in the uapi format is really unreliable. The vfs currently hacks around
directly in the uapi struct storing values that frankly the security and
integrity modules can't correctly interpret as evidenced by bugs we reported
and fixed in this area. It's not necessarily even their fault it's just that
the format we provide to them is sub optimal.
* Some filesystems like 9p and cifs need access to the dentry in order to get
and set posix acls which is why they either only partially or not even at all
implement get and set inode operations. For example, cifs allows setxattr()
and getxattr() operations but doesn't allow permission checking based on posix
acls because it can't implement a get acl inode operation.
Thus, this patch series updates the set acl inode operation to take a dentry
instead of an inode argument. However, for the get acl inode operation we
can't do this as the old get acl method is called in e.g.,
generic_permission() and inode_permission(). These helpers in turn are called
in various filesystem's permission inode operation. So passing a dentry
argument to the old get acl inode operation would amount to passing a dentry
to the permission inode operation which we shouldn't and probably can't do.
So instead of extending the existing inode operation Christoph suggested to
add a new one. He also requested to ensure that the get and set acl inode
operation taking a dentry are consistently named. So for this version the old
get acl operation is renamed to ->get_inode_acl() and a new ->get_acl() inode
operation taking a dentry is added. With this we can give both 9p and cifs get
and set acl inode operations and in turn remove their complex custom posix
xattr handlers.
In the future I hope to get rid of the inode method duplication but it isn't
like we have never had this situation. Readdir is just one example. And
frankly, the overall gain in type safety and the more pleasant api wise are
simply too big of a benefit to not accept this duplication for a while.
* We've done a full audit of every codepaths using variant of the current
generic xattr api to get and set posix acls and surprisingly it isn't
that many places. There's of course always a chance that we might have missed
some and if so I'm sure we'll find them soon enough.
The crucial codepaths to be converted are obviously stacking filesystems such
as ecryptfs and overlayfs.
For a list of all callers currently using generic xattr api helpers see [2]
including comments whether they support posix acls or not.
* The old vfs generic posix acl infrastructure doesn't obey the create and
replace semantics promised on the setxattr(2) manpage. This patch series
doesn't address this. It really is something we should revisit later though.
The patches in this PR are roughly organized as follows:
(1) Change existing set acl inode operation to take a dentry argument.
(Intended to be a non-functional change.)
(2) Rename existing get acl method.
(Intended to be a non-functional change.)
(3) Implement get and set acl inode operations for filesystems that couldn't
implement one before because of the missing dentry. That's mostly 9p and
cifs.
(Intended to be a non-functional change.)
(4) Build posix acl api, i.e., add vfs_get_acl(), vfs_remove_acl(), and
vfs_set_acl() including security and integrity hooks.
(Intended to be a non-functional change.)
(5) Implement get and set acl inode operations for stacking filesystems.
(Intended to be a non-functional change.)
(6) Switch posix acl handling in stacking filesystems to new posix acl api now
that all filesystems it can stack upon support it.
(7) Switch vfs to new posix acl api
(semantical change)
(8) Remove all now unused helpers
(9) Additional regression fixes reported after we merged this into linux-next
after v6.1-rc1:
e40df4281b86 orangefs: fix mode handling
5b52aebef895 ovl: call posix_acl_release() after error checking
16257cf6658d evm: remove dead code in evm_inode_set_acl()
cb2144d66b0b cifs: check whether acl is valid early
Thanks to Seth for a lot of good discussion around this and encouragement and
input from Christoph.
/* Testing */
clang: Ubuntu clang version 15.0.2-1
gcc: gcc (Ubuntu 12.2.0-3ubuntu1) 12.2.0
All patches are based on v6.2-rc1 and have been sitting in linux-next. No build
failures or warnings were observed. All old and new tests in fstests,
selftests, and LTP pass without regressions. But a series like this has of
course regression potential and it's almost impossible to run fstests for all
filesystems that are touched. For a bunch of them I wouldn't even know how to
test them. Even just runing orangefs was a lot of additional time and work. So
we'll need to watch out for any issues.
/* Conflicts */
Please note, that linux-next reported a build failure with the NTFS3 tree. The
NTFS3 tree contains changes to their POSIX ACL handling that rely on a helper
that got renamed in this series. Stephen reported and posted an accurate simple
patch to fix this. He suggested to simply point you to the reported failure and
the patch:
https://lore.kernel.org/lkml/20221115101756.5d311f25@xxxxxxxxxxxxxxxx
There were no merge conflicts when doing a test merge with current mainline
based on the v6.1 pushed yesterday.
mainline.
The following changes since commit 9abf2313adc1ca1b6180c508c25f22f9395cc780:
Linux 6.1-rc1 (2022-10-16 15:36:24 -0700)
are available in the Git repository at:
ssh://git@xxxxxxxxxxxxxxxxxxx/pub/scm/linux/kernel/git/vfs/idmapping.git tags/fs.acl.rework.v6.2
for you to fetch changes up to d6fdf29f7b99814d3673f2d9f4649262807cb836:
posix_acl: Fix the type of sentinel in get_acl (2022-12-02 10:01:28 +0100)
Please consider pulling these changes from the signed fs.acl.rework.v6.2 tag.
Thanks!
Christian
----------------------------------------------------------------
fs.acl.rework.v6.2
----------------------------------------------------------------
Christian Brauner (35):
orangefs: rework posix acl handling when creating new filesystem objects
fs: pass dentry to set acl method
fs: rename current get acl method
fs: add new get acl method
cifs: implement get acl method
cifs: implement set acl method
9p: implement get acl method
9p: implement set acl method
security: add get, remove and set acl hook
selinux: implement get, set and remove acl hook
smack: implement get, set and remove acl hook
integrity: implement get and set acl hook
evm: add post set acl hook
internal: add may_write_xattr()
acl: add vfs_set_acl()
acl: add vfs_get_acl()
acl: add vfs_remove_acl()
ksmbd: use vfs_remove_acl()
ecryptfs: implement get acl method
ecryptfs: implement set acl method
ovl: implement get acl method
ovl: implement set acl method
ovl: use posix acl api
xattr: use posix acl api
evm: remove evm_xattr_acl_change()
ecryptfs: use stub posix acl handlers
ovl: use stub posix acl handlers
cifs: use stub posix acl handlers
9p: use stub posix acl handlers
acl: remove a slew of now unused helpers
acl: make vfs_posix_acl_to_xattr() static
cifs: check whether acl is valid early
evm: remove dead code in evm_inode_set_acl()
ovl: call posix_acl_release() after error checking
orangefs: fix mode handling
Uros Bizjak (1):
posix_acl: Fix the type of sentinel in get_acl
Documentation/filesystems/locking.rst | 10 +-
Documentation/filesystems/porting.rst | 4 +-
Documentation/filesystems/vfs.rst | 5 +-
fs/9p/acl.c | 295 +++++++-------
fs/9p/acl.h | 8 +-
fs/9p/vfs_inode_dotl.c | 4 +
fs/9p/xattr.c | 7 +-
fs/9p/xattr.h | 2 -
fs/bad_inode.c | 4 +-
fs/btrfs/acl.c | 3 +-
fs/btrfs/ctree.h | 2 +-
fs/btrfs/inode.c | 8 +-
fs/ceph/acl.c | 3 +-
fs/ceph/dir.c | 2 +-
fs/ceph/inode.c | 4 +-
fs/ceph/super.h | 2 +-
fs/cifs/cifsacl.c | 139 +++++++
fs/cifs/cifsfs.c | 4 +
fs/cifs/cifsproto.h | 20 +-
fs/cifs/cifssmb.c | 206 ++++++----
fs/cifs/xattr.c | 68 +---
fs/ecryptfs/inode.c | 32 ++
fs/erofs/inode.c | 6 +-
fs/erofs/namei.c | 2 +-
fs/ext2/acl.c | 3 +-
fs/ext2/acl.h | 2 +-
fs/ext2/file.c | 2 +-
fs/ext2/inode.c | 2 +-
fs/ext2/namei.c | 4 +-
fs/ext4/acl.c | 3 +-
fs/ext4/acl.h | 2 +-
fs/ext4/file.c | 2 +-
fs/ext4/ialloc.c | 2 +-
fs/ext4/inode.c | 2 +-
fs/ext4/namei.c | 4 +-
fs/f2fs/acl.c | 4 +-
fs/f2fs/acl.h | 2 +-
fs/f2fs/file.c | 4 +-
fs/f2fs/namei.c | 4 +-
fs/fuse/acl.c | 3 +-
fs/fuse/dir.c | 4 +-
fs/fuse/fuse_i.h | 2 +-
fs/gfs2/acl.c | 3 +-
fs/gfs2/acl.h | 2 +-
fs/gfs2/inode.c | 6 +-
fs/internal.h | 21 +
fs/jffs2/acl.c | 3 +-
fs/jffs2/acl.h | 2 +-
fs/jffs2/dir.c | 2 +-
fs/jffs2/file.c | 2 +-
fs/jffs2/fs.c | 2 +-
fs/jfs/acl.c | 3 +-
fs/jfs/file.c | 4 +-
fs/jfs/jfs_acl.h | 2 +-
fs/jfs/namei.c | 2 +-
fs/ksmbd/smb2pdu.c | 8 +-
fs/ksmbd/smbacl.c | 6 +-
fs/ksmbd/vfs.c | 21 +-
fs/ksmbd/vfs.h | 4 +-
fs/namei.c | 4 +-
fs/nfs/nfs3_fs.h | 2 +-
fs/nfs/nfs3acl.c | 9 +-
fs/nfs/nfs3proc.c | 4 +-
fs/nfsd/nfs2acl.c | 8 +-
fs/nfsd/nfs3acl.c | 8 +-
fs/nfsd/nfs4acl.c | 4 +-
fs/nfsd/vfs.c | 4 +-
fs/ntfs3/file.c | 4 +-
fs/ntfs3/namei.c | 4 +-
fs/ntfs3/ntfs_fs.h | 4 +-
fs/ntfs3/xattr.c | 9 +-
fs/ocfs2/acl.c | 3 +-
fs/ocfs2/acl.h | 2 +-
fs/ocfs2/file.c | 4 +-
fs/ocfs2/namei.c | 2 +-
fs/orangefs/acl.c | 47 +--
fs/orangefs/inode.c | 54 ++-
fs/orangefs/namei.c | 2 +-
fs/orangefs/orangefs-kernel.h | 7 +-
fs/overlayfs/copy_up.c | 38 ++
fs/overlayfs/dir.c | 22 +-
fs/overlayfs/inode.c | 187 +++++++--
fs/overlayfs/overlayfs.h | 42 +-
fs/overlayfs/super.c | 107 +----
fs/posix_acl.c | 725 +++++++++++++++++-----------------
fs/reiserfs/acl.h | 6 +-
fs/reiserfs/file.c | 2 +-
fs/reiserfs/inode.c | 2 +-
fs/reiserfs/namei.c | 4 +-
fs/reiserfs/xattr_acl.c | 11 +-
fs/xattr.c | 85 ++--
fs/xfs/xfs_acl.c | 3 +-
fs/xfs/xfs_acl.h | 2 +-
fs/xfs/xfs_iops.c | 16 +-
include/linux/evm.h | 49 +++
include/linux/fs.h | 10 +-
include/linux/ima.h | 24 ++
include/linux/lsm_hook_defs.h | 6 +
include/linux/lsm_hooks.h | 12 +
include/linux/posix_acl.h | 41 +-
include/linux/posix_acl_xattr.h | 47 ++-
include/linux/security.h | 29 ++
include/linux/xattr.h | 6 +
mm/shmem.c | 2 +-
security/integrity/evm/evm_main.c | 146 ++++---
security/integrity/ima/ima_appraise.c | 9 +
security/security.c | 42 ++
security/selinux/hooks.c | 22 ++
security/smack/smack_lsm.c | 71 ++++
109 files changed, 1820 insertions(+), 1117 deletions(-)
