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c61ca55725
This issue came up with NFSv4 as the lower layer, which generates "system.nfs4_acl" xattrs (even for plain old unix permissions). Prior to this patch this prevented copy-up from succeeding. The overlayfs permission model mandates that permissions are checked locally for the task and remotely for the mounter(*). NFS4 ACLs are not supported by the Linux kernel currently, hence they cannot be enforced locally. Which means it is indifferent whether this attribute is copied or not. Generalize this to any xattr that is not used in access checking (i.e. it's not a POSIX ACL and not in the "security." namespace). Incidentally, best effort copying of xattrs seems to also be the behavior of "cp -a", which is what overlayfs tries to mimic. (*) Documentation/filesystems/overlayfs.txt#Permission model Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.