attribute namespace and DAC protection on file:
- Attribute names beginning with '$' are in the system namespace
- The attribute name "$" is reserved
- System namespace attributes may only be read/set by suser()
or by kernel (cred == NULL)
- Other attribute names are in the application namespace
- The attribute name "" is reserved
- Application namespace attributes are protected in the manner
of the target file permission
o Kernel changes
- Add ufs_extattr_valid_attrname() to check whether the requested
attribute "set" or "enable" is appropriate (i.e., non-reserved)
- Modify ufs_extattr_credcheck() to accept target file vnode, not
to take inode uid
- Modify ufs_extattr_credcheck() to check namespace, then enforce
either kernel/suser for system namespace, or vaccess() for
application namespace
o EA backing file format changes
- Remove permission fields from extended attribute backing file
header
- Bump extended attribute backing file header version to 3
o Update extattrctl.c and extattrctl.8
- Remove now deprecated -r and -w arguments to initattr, as
permissions are now implicit
- (unrelated) fix error reporting and unlinking during failed
initattr to remove duplicate/inaccurate error messages, and to
only unlink if the failure wasn't in the backing file open()
Obtained from: TrustedBSD Project
e6a536221c