linux: overlayfs: Add kernel patch resolving a file change notification issue

Add a temporary patch that resolves a file change notification issue
with overlayfs where IMA did not become aware of the file changes
since the 'lower' inode's i_version had not changed. The issue will be
resolved in later kernels with the following patch that builds on
newly addd feature (support for STATX_CHANGE_COOKIE) in v6.3-rc1:

https://lore.kernel.org/linux-integrity/20230418-engste-gastwirtschaft-601fb389bba5@brauner/T/#m3bf84296fe9e6499abb6e3191693948add2ff459

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>

2 files changed, 43 insertions, 0 deletions

diff --git a/meta-integrity/recipes-kernel/linux/linux/0001-ovl-Increment-iversion-upon-file-changes.patch b/meta-integrity/recipes-kernel/linux/linux/0001-ovl-Increment-iversion-upon-file-changes.patch
new file mode 100644
index 0000000..d2b5c28
--- /dev/null
+++ b/meta-integrity/recipes-kernel/linux/linux/0001-ovl-Increment-iversion-upon-file-changes.patch
@@ -0,0 +1,42 @@
+From e9ed62e8d1d3eee7ffe862d9812c5320d3b9bd88 Mon Sep 17 00:00:00 2001
+From: Stefan Berger <stefanb@linux.ibm.com>
+Date: Thu, 6 Apr 2023 11:27:29 -0400
+Subject: [PATCH] ovl: Increment iversion upon file changes
+
+This is a temporary patch for kernels that do not implement
+STATX_CHANGE_COOKIE (<= 6.2). The successor patch will be this one:
+
+https://lore.kernel.org/linux-integrity/20230418-engste-gastwirtschaft-601fb389bba5@brauner/T/#m3bf84296fe9e6499abb6e3191693948add2ff459
+
+Increment the lower inode's iversion for IMA to be able to recognize
+changes to the file.
+
+Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
+---
+ fs/overlayfs/file.c | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
+index 6011f955436b..1dfe5e7bfe1c 100644
+--- a/fs/overlayfs/file.c
++++ b/fs/overlayfs/file.c
+@@ -13,6 +13,7 @@
+ #include <linux/security.h>
+ #include <linux/mm.h>
+ #include <linux/fs.h>
++#include <linux/iversion.h>
+ #include "overlayfs.h"
+ 
+ struct ovl_aio_req {
+@@ -408,6 +409,8 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
+                if (ret != -EIOCBQUEUED)
+                        ovl_aio_cleanup_handler(aio_req);
+        }
++       if (ret > 0)
++               inode_maybe_inc_iversion(inode, false);
+ out:
+        revert_creds(old_cred);
+ out_fdput:
+-- 
+2.34.1
+
diff --git a/meta-integrity/recipes-kernel/linux/linux_ima.inc b/meta-integrity/recipes-kernel/linux/linux_ima.inc
index 0b6f530..9d48e5c 100644
--- a/meta-integrity/recipes-kernel/linux/linux_ima.inc
+++ b/meta-integrity/recipes-kernel/linux/linux_ima.inc
@@ -2,6 +2,7 @@ FILESEXTRAPATHS:append := "${THISDIR}/linux:"
 
 SRC_URI += " \
     ${@bb.utils.contains('DISTRO_FEATURES', 'ima', 'file://ima.scc', '', d)} \
+    file://0001-ovl-Increment-iversion-upon-file-changes.patch \
 "
 
 do_configure() {