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
