On 01/20/2015 06:17 PM, James Morris wrote: > On Sat, 17 Jan 2015, Ben Hutchings wrote: > >> chown() and write() should clear all privilege attributes on >> a file - setuid, setgid, setcap and any other extended >> privilege attributes. >> >> However, any attributes beyond setuid and setgid are managed by the >> LSM and not directly by the filesystem, so they cannot be set along >> with the other attributes. >> >> Currently we call security_inode_killpriv() in notify_change(), >> but in case of a chown() this is too early - we have not called >> inode_change_ok() or made any filesystem-specific permission/sanity >> checks. >> >> Add a new function setattr_killpriv() which calls >> security_inode_killpriv() if necessary, and change the setattr() >> implementation to call this in each filesystem that supports xattrs. >> This assumes that extended privilege attributes are always stored in >> xattrs. > > It'd be useful to get some input from LSM module maintainers on this. > > e.g. doesn't SELinux already handle this via policy directives? There have been a couple postings of a similar patch set [1] by Jan Kara, although I don't believe that series addressed chown(). If I am reading the patches correctly, they (correctly) don't affect SELinux or Smack labels; they are just calling the existing security_inode_killpriv() hook, which is only implemented for the capability module to remove the security.capability xattr. [1] http://marc.info/?l=linux-security-module&m=141890696325054&w=2 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
