linux-kernel - [PATCH -next 0/2] lsm: Change inode

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Date:   Fri, 5 May 2023 16:11:58 +0800
From:   Xiu Jianfeng <xiujianfeng@...wei.com>
To:     <gregkh@...uxfoundation.org>, <rafael@...nel.org>,
        <viro@...iv.linux.org.uk>, <brauner@...nel.org>,
        <dhowells@...hat.com>, <code@...icks.com>,
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        <gnoack3000@...il.com>, <roberto.sassu@...wei.com>
CC:     <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <linux-cachefs@...hat.com>, <ecryptfs@...r.kernel.org>,
        <linux-cifs@...r.kernel.org>, <linux-nfs@...r.kernel.org>,
        <linux-unionfs@...r.kernel.org>,
        <linux-security-module@...r.kernel.org>, <selinux@...r.kernel.org>,
        <wangweiyang2@...wei.com>
Subject: [PATCH -next 0/2] lsm: Change inode_setattr() to take struct

Hi,

I am working on adding xattr/attr support for landlock [1], so we can
control fs accesses such as chmod, chown, uptimes, setxattr, etc.. inside
landlock sandbox. the LSM hooks as following are invoved:
1.inode_setattr
2.inode_setxattr
3.inode_removexattr
4.inode_set_acl
5.inode_remove_acl
which are controlled by LANDLOCK_ACCESS_FS_WRITE_METADATA.

and
1.inode_getattr
2.inode_get_acl
3.inode_getxattr
4.inode_listxattr
which are controlled by LANDLOCK_ACCESS_FS_READ_METADATA

Some of these hooks only take struct dentry as a argument, However, for
path-based LSMs such Landlock, Apparmor and Tomoyo, struct path instead
of struct dentry required to make sense of attr/xattr accesses. So we
need to refactor these hooks to take a struct path argument.

This patchset only refators inode_setattr hook as part of whole work.

Also, I have a problem about file_dentry() in __file_remove_privs() of the
first patch, before changes in commit c1892c37769cf ("vfs: fix deadlock in
file_remove_privs() on overlayfs"), it gets dentry and inode as belows:

struct dentry *dentry = file->f_path.dentry;
struct inode *inode = d_inode(dentry);

That would be clear to change it to pass &file->f_path to
__remove_privs()->notify_change()->inode_setattr().
After that commit, it has been changed to:

struct dentry *dentry = file_dentry(file);
struct inode *inode = file_inode(file);

If I understand correctly, the dentry from file_dentry() maybe the upper
or the lower, it can be different from file->f_path.dentry. It can't just
go back to use &file->f_path otherwise the bug will come back for
overlayfs. So for such scenario, how to get a path from file if the file
maybe or not from overlayfs, and which kind of overlayfs path is ok for
Landlock?

Xiu Jianfeng (2):
  fs: Change notify_change() to take struct path argument
  lsm: Change inode_setattr hook to take struct path argument

 drivers/base/devtmpfs.c       |  5 +++--
 fs/attr.c                     |  7 ++++---
 fs/cachefiles/interface.c     |  4 ++--
 fs/coredump.c                 |  2 +-
 fs/ecryptfs/inode.c           | 18 +++++++++---------
 fs/fat/file.c                 |  2 +-
 fs/inode.c                    |  8 +++++---
 fs/ksmbd/smb2pdu.c            |  6 +++---
 fs/ksmbd/smbacl.c             |  2 +-
 fs/namei.c                    |  2 +-
 fs/nfsd/vfs.c                 | 12 ++++++++----
 fs/open.c                     | 19 ++++++++++---------
 fs/overlayfs/overlayfs.h      |  4 +++-
 fs/utimes.c                   |  2 +-
 include/linux/fs.h            |  4 ++--
 include/linux/lsm_hook_defs.h |  2 +-
 include/linux/security.h      |  4 ++--
 security/security.c           | 10 +++++-----
 security/selinux/hooks.c      |  3 ++-
 security/smack/smack_lsm.c    |  5 +++--
 20 files changed, 67 insertions(+), 54 deletions(-)

-- 
2.17.1