[PATCH] knfsd: nfsd4: acls: relax the nfsv4->posix mapping
Use a different nfsv4->(draft posix) acl mapping which is
1. completely backwards compatible,
2. accepts any nfsv4 acl, and
3. errs on the side of restricting permissions.
In detail:
1. completely backwards compatible: The new mapping produces the
same result on any acl produced by the existing (draft
posix)->nfsv4 mapping; the one exception is that we no longer
attempt to guess the value of the mask by assuming certain denies
represent the mask. Since the server still keeps track of the mask
locally, sequences of chmod's will still be handled fine; the only
thing this will change is sequences of chmod's with intervening
read-modify-writes of the acl. That last case just isn't worth the
trouble and the possible misrepresentations of the user's intent
(if we guess that a certain deny indicates masking is in effect
when it really isn't).
2. accepts any nfsv4 acl: That's not quite true: we still reject
acls that use combinations of inheritance flags that we don't
support. We also reject acls that attempt to explicitly deny
read_acl or read_attributes permissions, or that attempt to deny
write_acl or write_attributes permissions to the owner of the file.
3. errs on the side of restricting permissions: one exception to
this last rule: we totally ignore some bits (write_owner,
synchronize, read_named_attributes, etc.) that are completely alien
to our filesystem semantics, in some cases even if that would mean
ignoring an explicit deny that we have no intention of enforcing.
Excepting that, the posix acl produced should be the most
permissive acl that is not more permissive than the given nfsv4
acl.
And the new code's shorter, too. Neato.
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
1 file changed