Properly evaluate edge cases where user credential may grant capability
to override DAC in various situations. Switch to using ns-aware checks
rather than capable().
Expand optimization allow bypass of zfs_zaccess() in case of trivial
ACL if MAY_OPEN is included in requested mask. This will be evaluated
in generic_permission() check, which is RCU walk safe. This means that
in most cases evaluating permissions on boot volume with NFSv4 ACLs
will follow the fast path on checking inode permissions.
Additionally, CAP_SYS_ADMIN is granted to nfsd process, and so override
for this capability in access2 policy check is removed in favor of a
simple check for fsid == 0. Checks for CAP_DAC_OVERRIDE and other
override capabilities are kept as-is.
Signed-off-by: Andrew Walker <awalker@ixsystems.com>
39b4adf91d