linux-kernel - [PATCH v14 13/26] userns: Add pointer to ima_namespace to user

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Message-Id: <20220915193221.1728029-14-stefanb@linux.ibm.com>
Date:   Thu, 15 Sep 2022 15:32:08 -0400
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     linux-integrity@...r.kernel.org
Cc:     zohar@...ux.ibm.com, serge@...lyn.com, brauner@...nel.org,
        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,
        jpenumak@...hat.com, Stefan Berger <stefanb@...ux.ibm.com>
Subject: [PATCH v14 13/26] userns: Add pointer to ima_namespace to user_namespace

Add a pointer to ima_namespace to the user_namespace and initialize
the init_user_ns with a pointer to init_ima_ns. We need a pointer from
the user namespace to its associated IMA namespace since IMA namespaces
are piggybacking on user namespaces.

Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
Acked-by: Christian Brauner <brauner@...nel.org>
Reviewed-by: Mimi Zohar <zohar@...ux.ibm.com>

---
v13:
 - Added comment to ima_namespace pointer in user_namespace structure
   following Serge's suggestion

v11:
 - Added lost A-b from Christian back
 - Added sentence to patch description explaining why we need the pointer

v9:
 - Deferred implementation of ima_ns_from_user_ns() to later patch
---
 include/linux/ima.h            | 2 ++
 include/linux/user_namespace.h | 9 +++++++++
 kernel/user.c                  | 4 ++++
 3 files changed, 15 insertions(+)

diff --git a/include/linux/ima.h b/include/linux/ima.h
index 81708ca0ebc7..e0a17fda456a 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -14,6 +14,8 @@
 #include <crypto/hash_info.h>
 struct linux_binprm;
 
+extern struct ima_namespace init_ima_ns;
+
 #ifdef CONFIG_IMA
 extern enum hash_algo ima_get_current_hash_algo(void);
 extern int ima_bprm_check(struct linux_binprm *bprm);
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 33a4240e6a6f..8cb3489c988d 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -36,6 +36,7 @@ struct uid_gid_map { /* 64 bytes -- 1 cache line */
 #define USERNS_INIT_FLAGS USERNS_SETGROUPS_ALLOWED
 
 struct ucounts;
+struct ima_namespace;
 
 enum ucount_type {
 	UCOUNT_USER_NAMESPACES,
@@ -99,6 +100,14 @@ struct user_namespace {
 #endif
 	struct ucounts		*ucounts;
 	long ucount_max[UCOUNT_COUNTS];
+#ifdef CONFIG_IMA_NS
+	/* Pointer to ima_ns which this user_ns created.  Can be null. IMA's
+	 * file access checks will walk the userns->parent chain and check
+	 * against all active ima_ns's. Note that when the user_ns is
+	 * freed, the ima_ns is guaranteed to be free-able.
+	 */
+	struct ima_namespace	*ima_ns;
+#endif
 } __randomize_layout;
 
 struct ucounts {
diff --git a/kernel/user.c b/kernel/user.c
index e2cf8c22b539..e5d1f4b9b8ba 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -19,6 +19,7 @@
 #include <linux/export.h>
 #include <linux/user_namespace.h>
 #include <linux/proc_ns.h>
+#include <linux/ima.h>
 
 /*
  * userns count is 1 for root user, 1 for init_uts_ns,
@@ -67,6 +68,9 @@ struct user_namespace init_user_ns = {
 	.keyring_name_list = LIST_HEAD_INIT(init_user_ns.keyring_name_list),
 	.keyring_sem = __RWSEM_INITIALIZER(init_user_ns.keyring_sem),
 #endif
+#ifdef CONFIG_IMA_NS
+	.ima_ns = &init_ima_ns,
+#endif
 };
 EXPORT_SYMBOL_GPL(init_user_ns);
 
-- 
2.36.1