Re: [PATCH v8 13/19] ima: Add functions for creation and freeing of an ima_namespace

[Christian Brauner <brauner@kernel.org>]

On Tue, Jan 04, 2022 at 12:04:10PM -0500, Stefan Berger wrote:
> From: Stefan Berger <stefanb@linux.ibm.com>
> 
> Implement create_ima_ns() to create and initialize an ima_namespace
> and implement free_ima_ns() to free it.
> 
> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
> ---
>  include/linux/ima.h                      | 13 +++++
>  security/integrity/ima/Makefile          |  1 +
>  security/integrity/ima/ima.h             | 16 +++++++
>  security/integrity/ima/ima_init_ima_ns.c |  2 +-
>  security/integrity/ima/ima_ns.c          | 61 ++++++++++++++++++++++++
>  5 files changed, 92 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 e1d65162d1fb..06c88cb17b21 100644
> --- a/include/linux/ima.h
> +++ b/include/linux/ima.h
> @@ -226,4 +226,17 @@ 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 f63c6f22b853..4255301e5b96 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -163,6 +163,7 @@ 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,
> @@ -503,4 +504,19 @@ static inline struct ima_namespace *get_current_ns(void)
>  	return &init_ima_ns;
>  }
>  
> +#ifdef CONFIG_IMA_NS
> +
> +struct ima_namespace *create_ima_ns(struct user_namespace *user_ns);
> +
> +#else
> +
> +static inline struct ima_namespace *
> +create_ima_ns(struct user_namespace *user_ns)

Why are you introducing these functions in 13/19 when you're first using
it in the last patch of this series?

> +{
> +	WARN(1, "Cannot create an IMA namespace\n");
> +	return ERR_PTR(-EFAULT);
> +}

I think I pointed this out earlier or made illustrated it in my draft
patch earlier. This function should not return a ptr to an ima
namespace. That's just not necessary: the ima namespace _is stashed in
struct user namespace_:

static int create_ima_ns(struct uesr_namespace *user_ns)
{
	[...]

	/* Pairs with [...] */
	smp_store_release(&user_ns->ima_ns, ns);
	return 0;
}

and in the other case:

static inline create_ima_ns(struct user_namespace *user_ns)
{
	return -EINVAL;
}