This is a note to let you know that I've just added the patch titled
ima: detect changes to the backing overlay file
to the 6.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ima-detect-changes-to-the-backing-overlay-file.patch
and it can be found in the queue-6.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b836c4d29f2744200b2af41e14bf50758dddc818 Mon Sep 17 00:00:00 2001
From: Mimi Zohar <zohar@xxxxxxxxxxxxx>
Date: Wed, 18 Oct 2023 14:47:02 -0400
Subject: ima: detect changes to the backing overlay file
From: Mimi Zohar <zohar@xxxxxxxxxxxxx>
commit b836c4d29f2744200b2af41e14bf50758dddc818 upstream.
Commit 18b44bc5a672 ("ovl: Always reevaluate the file signature for
IMA") forced signature re-evaulation on every file access.
Instead of always re-evaluating the file's integrity, detect a change
to the backing file, by comparing the cached file metadata with the
backing file's metadata. Verifying just the i_version has not changed
is insufficient. In addition save and compare the i_ino and s_dev
as well.
Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
Tested-by: Eric Snowberg <eric.snowberg@xxxxxxxxxx>
Tested-by: Raul E Rangel <rrangel@xxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/overlayfs/super.c | 2 +-
security/integrity/ima/ima_api.c | 5 +++++
security/integrity/ima/ima_main.c | 16 +++++++++++++++-
security/integrity/integrity.h | 2 ++
4 files changed, 23 insertions(+), 2 deletions(-)
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1467,7 +1467,7 @@ int ovl_fill_super(struct super_block *s
ovl_trusted_xattr_handlers;
sb->s_fs_info = ofs;
sb->s_flags |= SB_POSIXACL;
- sb->s_iflags |= SB_I_SKIP_SYNC | SB_I_IMA_UNVERIFIABLE_SIGNATURE;
+ sb->s_iflags |= SB_I_SKIP_SYNC;
err = -ENOMEM;
root_dentry = ovl_get_root(sb, ctx->upper.dentry, oe);
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -243,6 +243,7 @@ int ima_collect_measurement(struct integ
{
const char *audit_cause = "failed";
struct inode *inode = file_inode(file);
+ struct inode *real_inode = d_real_inode(file_dentry(file));
const char *filename = file->f_path.dentry->d_name.name;
struct ima_max_digest_data hash;
struct kstat stat;
@@ -302,6 +303,10 @@ int ima_collect_measurement(struct integ
iint->ima_hash = tmpbuf;
memcpy(iint->ima_hash, &hash, length);
iint->version = i_version;
+ if (real_inode != inode) {
+ iint->real_ino = real_inode->i_ino;
+ iint->real_dev = real_inode->i_sb->s_dev;
+ }
/* Possibly temporary failure due to type of read (eg. O_DIRECT) */
if (!result)
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -25,6 +25,7 @@
#include <linux/xattr.h>
#include <linux/ima.h>
#include <linux/fs.h>
+#include <linux/iversion.h>
#include "ima.h"
@@ -207,7 +208,7 @@ static int process_measurement(struct fi
u32 secid, char *buf, loff_t size, int mask,
enum ima_hooks func)
{
- struct inode *inode = file_inode(file);
+ struct inode *backing_inode, *inode = file_inode(file);
struct integrity_iint_cache *iint = NULL;
struct ima_template_desc *template_desc = NULL;
char *pathbuf = NULL;
@@ -284,6 +285,19 @@ static int process_measurement(struct fi
iint->measured_pcrs = 0;
}
+ /* Detect and re-evaluate changes made to the backing file. */
+ backing_inode = d_real_inode(file_dentry(file));
+ if (backing_inode != inode &&
+ (action & IMA_DO_MASK) && (iint->flags & IMA_DONE_MASK)) {
+ if (!IS_I_VERSION(backing_inode) ||
+ backing_inode->i_sb->s_dev != iint->real_dev ||
+ backing_inode->i_ino != iint->real_ino ||
+ !inode_eq_iversion(backing_inode, iint->version)) {
+ iint->flags &= ~IMA_DONE_MASK;
+ iint->measured_pcrs = 0;
+ }
+ }
+
/* Determine if already appraised/measured based on bitmask
* (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
* IMA_AUDIT, IMA_AUDITED)
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -164,6 +164,8 @@ struct integrity_iint_cache {
unsigned long flags;
unsigned long measured_pcrs;
unsigned long atomic_flags;
+ unsigned long real_ino;
+ dev_t real_dev;
enum integrity_status ima_file_status:4;
enum integrity_status ima_mmap_status:4;
enum integrity_status ima_bprm_status:4;
Patches currently in stable-queue which might be from zohar@xxxxxxxxxxxxx are
queue-6.5/ima-annotate-iint-mutex-to-avoid-lockdep-false-positive-warnings.patch
queue-6.5/ima-detect-changes-to-the-backing-overlay-file.patch
