Quoting Stefan Berger (stef...@linux.vnet.ibm.com):
> On 07/11/2017 01:12 PM, Serge E. Hallyn wrote:
> >>diff --git a/fs/xattr.c b/fs/xattr.c
> >>index 464c94b..eacad9e 100644
> >>--- a/fs/xattr.c
> >>+++ b/fs/xattr.c
> >>@@ -133,20 +133,440 @@ xattr_permission(struct inode *inode, const char
> >>*name, int mask)
> >> return inode_permission(inode, mask);
> >> }
> >>+/*
> >>+ * A list of extended attributes that are supported in user namespaces
> >>+ */
> >>+static const char *const userns_xattrs[] = {
> >>+ XATTR_NAME_CAPS,
> >>+ NULL
> >>+};
> >>+
> >>+/*
> >>+ * xattrs_is_userns_supported - Check whether an xattr is supported in
> >>userns
> >>+ *
> >>+ * @name: full name of the extended attribute
> >>+ * @prefix: do a prefix match (true) or a full match (false)
> >>+ *
> >>+ * This function returns < 0 if not supported, an index into
> >>userns_xattrs[]
> >>+ * otherwise.
> >>+ */
> >>+static int
> >>+xattr_is_userns_supported(const char *name, int prefix)
> >>+{
> >>+ int i;
> >>+
> >>+ if (!name)
> >>+ return -1;
> >>+
> >>+ for (i = 0; userns_xattrs[i]; i++) {
> >>+ if (prefix) {
> >>+ if (!strncmp(userns_xattrs[i], name,
> >>+ strlen(userns_xattrs[i])))
> >>+ return i;
> >I think you here need to also check that the next char is either
> >'\0' or '.' (or maybe '@')
>
> I have the checks for '@' and '\0' done by the caller. With the
> current support of only security.capability I don't think we need to
> check for '.'.
Ah - ok, thanks.
