linux-kernel - [RFC 10/20] ima: Implement hierarchical processing of file accesses

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Message-Id: <20211130160654.1418231-11-stefanb@linux.ibm.com>
Date:   Tue, 30 Nov 2021 11:06:44 -0500
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     linux-integrity@...r.kernel.org
Cc:     zohar@...ux.ibm.com, serge@...lyn.com,
        christian.brauner@...ntu.com, containers@...ts.linux.dev,
        dmitry.kasatkin@...il.com, ebiederm@...ssion.com,
        krzysztof.struczynski@...wei.com, roberto.sassu@...wei.com,
        mpeters@...hat.com, lhinds@...hat.com, lsturman@...hat.com,
        puiterwi@...hat.com, jejb@...ux.ibm.com, jamjoom@...ibm.com,
        linux-kernel@...r.kernel.org, paul@...l-moore.com, rgb@...hat.com,
        linux-security-module@...r.kernel.org, jmorris@...ei.org,
        Stefan Berger <stefanb@...ux.ibm.com>
Subject: [RFC 10/20] ima: Implement hierarchical processing of file accesses

Implement hierarchical processing of file accesses in IMA namespaces by
walking the list of IMA namespaces towards the init_ima_ns. This way
file accesses can be audited in an IMA namespace and also be evaluated
against the IMA policies of parent IMA namespaces.

Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
---
 security/integrity/ima/ima_main.c | 29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index d692c9d53a98..42cbcaf2dc1e 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -199,10 +199,10 @@ void ima_file_free(struct file *file)
 	ima_check_last_writer(iint, inode, file);
 }
 
-static int process_measurement(struct ima_namespace *ns,
-			       struct file *file, const struct cred *cred,
-			       u32 secid, char *buf, loff_t size, int mask,
-			       enum ima_hooks func)
+static int _process_measurement(struct ima_namespace *ns,
+				struct file *file, const struct cred *cred,
+				u32 secid, char *buf, loff_t size, int mask,
+				enum ima_hooks func)
 {
 	struct inode *inode = file_inode(file);
 	struct integrity_iint_cache *iint = NULL;
@@ -404,6 +404,27 @@ static int process_measurement(struct ima_namespace *ns,
 	return 0;
 }
 
+static int process_measurement(struct ima_namespace *ns,
+			       struct file *file, const struct cred *cred,
+			       u32 secid, char *buf, loff_t size, int mask,
+			       enum ima_hooks func)
+{
+	int ret = 0;
+	struct user_namespace *user_ns;
+
+	do {
+		ret = _process_measurement(ns, file, cred, secid, buf, size, mask, func);
+		if (ret)
+			break;
+		user_ns = ns->user_ns->parent;
+		if (!user_ns)
+			break;
+		ns = user_ns->ima_ns;
+	} while (1);
+
+	return ret;
+}
+
 /**
  * ima_file_mmap - based on policy, collect/store measurement.
  * @file: pointer to the file to be measured (May be NULL)
-- 
2.31.1