On 12/8/21 06:54, Christian Brauner wrote:

On Wed, Dec 08, 2021 at 12:29:18PM +0100, Christian Brauner wrote:

quoted

On Tue, Dec 07, 2021 at 03:21:12PM -0500, Stefan Berger wrote:

quoted

Implement an IMA namespace data structure that gets created alongside a
user namespace with CLONE_NEWUSER. This lays down the foundation for
namespacing the different aspects of IMA (eg. IMA-audit, IMA-measurement,
IMA-appraisal).

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Suggested-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
  include/linux/ima.h                      | 59 +++++++++++++++++
  include/linux/user_namespace.h           |  4 ++
  init/Kconfig                             | 10 +++
  kernel/user.c                            |  9 ++-
  kernel/user_namespace.c                  | 16 +++++
  security/integrity/ima/Makefile          |  3 +-
  security/integrity/ima/ima.h             |  4 ++
  security/integrity/ima/ima_init.c        |  4 ++
  security/integrity/ima/ima_init_ima_ns.c | 32 +++++++++
  security/integrity/ima/ima_ns.c          | 82 ++++++++++++++++++++++++
  10 files changed, 221 insertions(+), 2 deletions(-)
  create mode 100644 security/integrity/ima/ima_init_ima_ns.c
  create mode 100644 security/integrity/ima/ima_ns.c

diff --git a/include/linux/ima.h b/include/linux/ima.h
index b6ab66a546ae..86d126b9ff2f 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h

@@ -11,6 +11,7 @@
  #include <linux/fs.h>
  #include <linux/security.h>
  #include <linux/kexec.h>
+#include <linux/user_namespace.h>
  #include <crypto/hash_info.h>
  struct linux_binprm;
  

@@ -210,6 +211,64 @@ static inline int ima_inode_removexattr(struct dentry *dentry,
  }
  #endif /* CONFIG_IMA_APPRAISE */
  
+struct ima_namespace {
+	struct kref kref;
+	struct user_namespace *user_ns;
+};
+
+extern struct ima_namespace init_ima_ns;
+
+#ifdef CONFIG_IMA_NS
+
+void free_ima_ns(struct kref *kref);
+
+static inline struct ima_namespace *get_ima_ns(struct ima_namespace *ns)
+{
+	if (ns)
+		kref_get(&ns->kref);
+
+	return ns;
+}
+
+static inline void put_ima_ns(struct ima_namespace *ns)
+{
+	if (ns) {
+		pr_debug("DEREF   ima_ns: 0x%p  ctr: %d\n", ns, kref_read(&ns->kref));
+		kref_put(&ns->kref, free_ima_ns);
+	}
+}
+
+struct ima_namespace *copy_ima_ns(struct ima_namespace *old_ns,
+				  struct user_namespace *user_ns);
+
+static inline struct ima_namespace *get_current_ns(void)
+{
+	return current_user_ns()->ima_ns;
+}
+
+#else
+
+static inline struct ima_namespace *get_ima_ns(struct ima_namespace *ns)
+{
+	return ns;
+}
+
+static inline void put_ima_ns(struct ima_namespace *ns)
+{
+}
+
+static inline struct ima_namespace *copy_ima_ns(struct ima_namespace *old_ns,
+						struct user_namespace *user_ns)
+{
+	return old_ns;
+}
+
+static inline struct ima_namespace *get_current_ns(void)
+{
+	return &init_ima_ns;
+}
+#endif /* CONFIG_IMA_NS */
+
  #if defined(CONFIG_IMA_APPRAISE) && defined(CONFIG_INTEGRITY_TRUSTED_KEYRING)
  extern bool ima_appraise_signature(enum kernel_read_file_id func);
  #else

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 33a4240e6a6f..5249db04d62b 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 +100,9 @@ struct user_namespace {
  #endif
  	struct ucounts		*ucounts;
  	long ucount_max[UCOUNT_COUNTS];
+#ifdef CONFIG_IMA
+	struct ima_namespace	*ima_ns;
+#endif
  } __randomize_layout;
  
  struct ucounts {

diff --git a/init/Kconfig b/init/Kconfig
index 11f8a845f259..27890607e8cb 100644
--- a/init/Kconfig
+++ b/init/Kconfig

@@ -1242,6 +1242,16 @@ config NET_NS
  	  Allow user space to create what appear to be multiple instances
  	  of the network stack.
  
+config IMA_NS
+	bool "IMA namespace"
+	depends on USER_NS
+	depends on IMA
+	default y
+	help
+	  Allow the creation of IMA namespaces for each user namespace.
+	  Namespaced IMA enables having IMA features work separately
+	  in each IMA namespace.
+
  endif # NAMESPACES
  
  config CHECKPOINT_RESTORE

diff --git a/kernel/user.c b/kernel/user.c
index e2cf8c22b539..b5dc803a033d 100644
--- a/kernel/user.c
+++ b/kernel/user.c

@@ -20,6 +20,10 @@
  #include <linux/user_namespace.h>
  #include <linux/proc_ns.h>
  
+#ifdef CONFIG_IMA
+extern struct ima_namespace init_ima_ns;
+#endif
+
  /*
   * userns count is 1 for root user, 1 for init_uts_ns,
   * and 1 for... ?

@@ -55,7 +59,7 @@ struct user_namespace init_user_ns = {
  			},
  		},
  	},
-	.ns.count = REFCOUNT_INIT(3),
+	.ns.count = REFCOUNT_INIT(4),
  	.owner = GLOBAL_ROOT_UID,
  	.group = GLOBAL_ROOT_GID,
  	.ns.inum = PROC_USER_INIT_INO,

@@ -67,6 +71,9 @@ 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
+	.ima_ns = &init_ima_ns,
+#endif
  };
  EXPORT_SYMBOL_GPL(init_user_ns);
  

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 6b2e3ca7ee99..c26885343b19 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c

@@ -20,6 +20,7 @@
  #include <linux/fs_struct.h>
  #include <linux/bsearch.h>
  #include <linux/sort.h>
+#include <linux/ima.h>
  
  static struct kmem_cache *user_ns_cachep __read_mostly;
  static DEFINE_MUTEX(userns_state_mutex);

@@ -141,8 +142,20 @@ int create_user_ns(struct cred *new)
  	if (!setup_userns_sysctls(ns))
  		goto fail_keyring;
  
+#if CONFIG_IMA
+	ns->ima_ns = copy_ima_ns(parent_ns->ima_ns, ns);
+	if (IS_ERR(ns->ima_ns)) {
+		ret = PTR_ERR(ns->ima_ns);
+		goto fail_userns_sysctls;
+	}
+#endif
+
  	set_cred_user_ns(new, ns);
  	return 0;
+#if CONFIG_IMA
+fail_userns_sysctls:
+	retire_userns_sysctls(ns);
+#endif

If you rewrite copy_ima_ns() put_ima_ns() a little you can remove all
the ifdefs in here and make this patch tiny.

Make copy_ima_ns() return an int. Afaict, you can remove passing the
parent ima_ns completely but if you have to pass through the
parent_userns.
Then you can initialize new_userns->ima_ns inside of copy_ima_ns() and
the ifdef will only need to be visible inside copy_ima_ns() and not in
create_user_ns(). Similar put_ima_ns() is only called in a single place
namely kernel/user_namespace.c. Make it take a user_namespace argument
and you can remove the ifdef in __put_user_ns() for put_ima_ns() too.

So something -- COMPLETELY UNTESTED -- like the below should work:

Thanks. I did this now for v5.

    Stefan