Quoting Stephen Smalley (2018-09-21 07:40:58) > If we set the inode sid to the superblock def_sid on an invalid > context, then we lose the association to the original context value. > The support for deferred mapping of contexts requires allocating a new > SID for the invalid context and storing that SID in the inode, so that > if the context later becomes valid upon a policy update/reload, the > inode SID will refer to the now valid context. > To combine the two, we would need security_context_to_sid_core() to > save the def_sid in the context structure for invalid contexts, and > change sidtab_search_core() to use that value instead of > SECINITSID_UNLABELED for invalid SIDs. Then the inode would be > treated as having the defcontext for access control and getxattr() w/o > CAP_MAC_ADMIN purposes, but a subsequent policy update/reload that > makes the context valid would automatically cause subsequent accesses > to the inode to start using the original context value for access > control and getxattr() purposes. I think that's the behavior you > want. > While implementing the change I've realized that storing default context for sidtab_search_core() in the context structure is not enough to achieve the desired behavior. The same invalid context may exist in two mounts with different 'defcontext', so default context can't be a property of a context structure. One way to address it is to propagate default context to sidtab_search() all the way from inode hooks. But that will be a bit intrusive. Something like avc_has_perm_default() will need to be added. Other way is to check for context validity in inode hooks and provide a default context to avc_has_perm() if the inode's sid is invalid. But this may have performance implication since validity check will be done each time in fast path. Do you see any other options? _______________________________________________ Selinux mailing list Selinux@xxxxxxxxxxxxx To unsubscribe, send email to Selinux-leave@xxxxxxxxxxxxx. To get help, send an email containing "help" to Selinux-request@xxxxxxxxxxxxx.
