xattr: switch to CLASS(fd)

commit a71874379ec8c6e788a61d71b3ad014a8d9a5c08 upstream.

BUG=b/492102770
TEST=presubmit
RELEASE_NOTE=Fixed CVE-2024-14027 in the Linux kernel.

cos-patch: security-moderate
Reviewed-by: Christian Brauner <brauner@kernel.org>
Change-Id: If9f28e0909f150c74c0d80d1b595a0575ebefe6f
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kernel CVE Triage Automation <cloud-image-kernel-cve-triage-automation@prod.google.com>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/141203
Reviewed-by: Kevin Liu <zhihuil@google.com>
Reviewed-by: Chenglong Tang <chenglongtang@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>