nfsd4: don't create unnecessary mask acl

Any setattr of the ACL attribute, even if it sets just the basic 3-ACE
ACL exactly as it was returned from a file with only mode bits, creates
a mask entry, and it is only the mask, not group, entry that is changed
by subsequent modifications of the mode bits.

So, for example, it's surprising that GROUP@ is left without read or
write permissions after a chmod 0666:

  touch test
  chmod 0600 test
  nfs4_getfacl test
        A::OWNER@:rwatTcCy
        A::GROUP@:tcy
        A::EVERYONE@:tcy
  nfs4_getfacl test | nfs4_setfacl -S - test #
  chmod 0666 test
  nfs4_getfacl test
        A::OWNER@:rwatTcCy
        A::GROUP@:tcy
        D::GROUP@:rwa
        A::EVERYONE@:rwatcy

So, let's stop creating the unnecessary mask ACL.

A mask will still be created on non-trivial ACLs (ACLs with actual named
user and group ACEs), so the odd posix-acl behavior of chmod modifying
only the mask will still be left in that case; but that's consistent
with local behavior.

Reported-by: Soumya Koduri <skoduri@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/fs/nfsd/nfs4acl.c b/fs/nfsd/nfs4acl.c
index d190e33..6f3f392 100644 (file)
--- a/fs/nfsd/nfs4acl.c
+++ b/fs/nfsd/nfs4acl.c
@@ -542,7 +542,10 @@ posix_state_to_acl(struct posix_acl_state *state, unsigned int flags)
         * up setting a 3-element effective posix ACL with all
         * permissions zero.
         */
-       nace = 4 + state->users->n + state->groups->n;
+       if (!state->users->n && !state->groups->n)
+               nace = 3;
+       else /* Note we also include a MASK ACE in this case: */
+               nace = 4 + state->users->n + state->groups->n;
        pacl = posix_acl_alloc(nace, GFP_KERNEL);
        if (!pacl)
                return ERR_PTR(-ENOMEM);
@@ -586,9 +589,11 @@ posix_state_to_acl(struct posix_acl_state *state, unsigned int flags)
                add_to_mask(state, &state->groups->aces[i].perms);
        }
 
-       pace++;
-       pace->e_tag = ACL_MASK;
-       low_mode_from_nfs4(state->mask.allow, &pace->e_perm, flags);
+       if (!state->users->n && !state->groups->n) {
+               pace++;
+               pace->e_tag = ACL_MASK;
+               low_mode_from_nfs4(state->mask.allow, &pace->e_perm, flags);
+       }
 
        pace++;
        pace->e_tag = ACL_OTHER;