On Fri, Oct 27, 2017 at 6:03 PM, David Howells <dhowells@xxxxxxxxxx> wrote: > Miklos Szeredi <mszeredi@xxxxxxxxxx> wrote: > >> Yes I did mean vfs_parse_sb_flag_option(). >> >> Yes, I understand its purpose, but it would be cleaner if all the >> option parsing was done in fc->ops->parse_option(). >> >> It might be worth introducing the vfs_parse_sb_flag_option(), to be >> called from ->parse_option(). > > I was trying to relieve the filesystem of the requirement to have to deal with > common stuff and also the need to talk directly to the LSM. No need to talk directly to the LSM: security_fs_context_parse_option() will do that in VFS code. How common is common stuff? dirsync/sync/rw: not handled by all filesystems, those that don't handle it should reject the option on the new interface lazytime: handled by generic code, AFAICS, but makes no sense on read-only fs so those should probably reject it mand: handled by generic code, but does not make sense for some filesystems (e.g. those that don't have all the unixy permission bits). posixacl: there's no such mount option now. The options is "acl" and does not get translated to MS_POSIXACL in mount(8). Makes zero sense to add a previously nonexistent option to the new interface. silent: makes no sense on the new interface, since we should no longer be putting error messages into the kernel log. So that leaves async/ro/nolazytime/nomand options to be handled by all filesystems. Not sure how to best handle these differences, but the current code definitely seems lacking, and I cannot imagine a better way than to pass all options to filesystem's ->parse_option() and add helper(s) to handle the generic options. >> > Btw, how would it affect the LSM? >> >> LSM would have to reject a "reset" if not enough privileges to >> *create* a new fs instance, since it essentially requires creating a >> new config, which is what is done when creating an fs instance. > > That's not what I'm asking. Would the reset change LSM state? Reset security > labels and options? No. And it wouldn't reset any other option that is immutable (e.g. server IP address). Thanks, Miklos
