Re: [PATCH v10 17/27] ima: Add functions for creating and freeing of an ima_namespace

[Mimi Zohar <zohar@linux.ibm.com>]

On Tue, 2022-02-01 at 15:37 -0500, Stefan Berger wrote:
> Implement create_ima_ns() to create an empty ima_namespace. Defer its
> initialization to a later point outside this function. Implement
> free_ima_ns() to free it.
> 
> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
> Acked-by: Christian Brauner <brauner@kernel.org>
> 
> ---
> v9:
>  - Set user_ns->ims_ns = NULL in free_ima_ns()
>  - Refactored create_ima_ns() to defer initialization
>  - Removed pr_debug functions
> ---
>  include/linux/ima.h                      | 13 ++++++
>  security/integrity/ima/Makefile          |  1 +
>  security/integrity/ima/ima.h             | 15 +++++++
>  security/integrity/ima/ima_init_ima_ns.c |  2 +-
>  security/integrity/ima/ima_ns.c          | 53 ++++++++++++++++++++++++
>  5 files changed, 83 insertions(+), 1 deletion(-)
>  create mode 100644 security/integrity/ima/ima_ns.c
> 
> diff --git a/include/linux/ima.h b/include/linux/ima.h
> index 0cf2a80c8b35..964a08702573 100644
> --- a/include/linux/ima.h
> +++ b/include/linux/ima.h
> @@ -220,4 +220,17 @@ static inline bool ima_appraise_signature(enum kernel_read_file_id func)
>  	return false;
>  }
>  #endif /* CONFIG_IMA_APPRAISE && CONFIG_INTEGRITY_TRUSTED_KEYRING */
> +
> +#ifdef CONFIG_IMA_NS
> +
> +void free_ima_ns(struct user_namespace *ns);
> +
> +#else
> +
> +static inline void free_ima_ns(struct user_namespace *user_ns)
> +{
> +}
> +
> +#endif /* CONFIG_IMA_NS */
> +
>  #endif /* _LINUX_IMA_H */
> diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
> index f8a5e5f3975d..b86a35fbed60 100644
> --- a/security/integrity/ima/Makefile
> +++ b/security/integrity/ima/Makefile
> @@ -14,6 +14,7 @@ ima-$(CONFIG_HAVE_IMA_KEXEC) += ima_kexec.o
>  ima-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o
>  ima-$(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) += ima_asymmetric_keys.o
>  ima-$(CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS) += ima_queue_keys.o
> +ima-$(CONFIG_IMA_NS) += ima_ns.o
>  
>  ifeq ($(CONFIG_EFI),y)
>  ima-$(CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT) += ima_efi.o
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index 8c757223d549..751e936a6311 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -167,6 +167,7 @@ extern bool ima_canonical_fmt;
>  int ima_init(void);
>  int ima_fs_init(void);
>  int ima_ns_init(void);
> +int ima_init_namespace(struct ima_namespace *ns);
>  int ima_add_template_entry(struct ima_namespace *ns,
>  			   struct ima_template_entry *entry, int violation,
>  			   const char *op, struct inode *inode,
> @@ -502,4 +503,18 @@ static inline struct ima_namespace
>  	return NULL;
>  }
>  
> +#ifdef CONFIG_IMA_NS
> +
> +struct ima_namespace *create_ima_ns(void);
> +
> +#else
> +
> +static inline struct ima_namespace *create_ima_ns(void)
> +{
> +	WARN(1, "Cannot create an IMA namespace\n");
> +	return ERR_PTR(-EFAULT);
> +}
> +
> +#endif /* CONFIG_IMA_NS */
> +
>  #endif /* __LINUX_IMA_H */
> diff --git a/security/integrity/ima/ima_init_ima_ns.c b/security/integrity/ima/ima_init_ima_ns.c
> index 1cba545ae477..166dab4a3126 100644
> --- a/security/integrity/ima/ima_init_ima_ns.c
> +++ b/security/integrity/ima/ima_init_ima_ns.c
> @@ -8,7 +8,7 @@
>  
>  #include "ima.h"
>  
> -static int ima_init_namespace(struct ima_namespace *ns)
> +int ima_init_namespace(struct ima_namespace *ns)
>  {
>  	int rc;
>  
> diff --git a/security/integrity/ima/ima_ns.c b/security/integrity/ima/ima_ns.c
> new file mode 100644
> index 000000000000..b3b81a1e313e
> --- /dev/null
> +++ b/security/integrity/ima/ima_ns.c
> @@ -0,0 +1,53 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2016-2021 IBM Corporation
> + * Author:
> + *  Yuqiong Sun <suny@us.ibm.com>
> + *  Stefan Berger <stefanb@linux.vnet.ibm.com>
> + */
> +
> +#include <linux/ima.h>
> +
> +#include "ima.h"
> +
> +static struct kmem_cache *imans_cachep;
> +
> +struct ima_namespace *create_ima_ns(void)
> +{
> +	struct ima_namespace *ns;
> +
> +	ns = kmem_cache_zalloc(imans_cachep, GFP_KERNEL);
> +	if (!ns)
> +		return ERR_PTR(-ENOMEM);
> +
> +	return ns;
> +}
> +
> +/* destroy_ima_ns() must only be called after ima_init_namespace() was called */
> +static void destroy_ima_ns(struct ima_namespace *ns)
> +{
> +	unregister_blocking_lsm_notifier(&ns->ima_lsm_policy_notifier);
> +	kfree(ns->arch_policy_entry);

Oh!  Here's the missing free of the architecture specific rules
(comment on 16/27).  Even if these rules have already been freed after
a custom policy is loaded, I guess it is safe to free them again.

Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>

> +	ima_free_policy_rules(ns);
> +}
> +
> +void free_ima_ns(struct user_namespace *user_ns)
> +{
> +	struct ima_namespace *ns = user_ns->ima_ns;
> +
> +	if (!ns || WARN_ON(ns == &init_ima_ns))
> +		return;
> +
> +	destroy_ima_ns(ns);
> +
> +	kmem_cache_free(imans_cachep, ns);
> +
> +	user_ns->ima_ns = NULL;
> +}
> +
> +static int __init imans_cache_init(void)
> +{
> +	imans_cachep = KMEM_CACHE(ima_namespace, SLAB_PANIC);
> +	return 0;
> +}
> +subsys_initcall(imans_cache_init)