Re: [PATCH v5 22/23] integrity: Move integrity functions to the LSM infrastructure

[Casey Schaufler]

On 11/7/2023 5:40 AM, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
>
> Remove hardcoded calls to integrity functions from the LSM infrastructure
> and, instead, register them in integrity_lsm_init() with the IMA or EVM
> LSM ID (the first non-NULL returned by ima_get_lsm_id() and
> evm_get_lsm_id()).
>
> Also move the global declaration of integrity_inode_get() to
> security/integrity/integrity.h, so that the function can be still called by
> IMA.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>

Reviewed-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>


> ---
>  include/linux/integrity.h      | 26 --------------------------
>  security/integrity/iint.c      | 30 +++++++++++++++++++++++++++++-
>  security/integrity/integrity.h |  7 +++++++
>  security/security.c            |  9 +--------
>  4 files changed, 37 insertions(+), 35 deletions(-)
>
> diff --git a/include/linux/integrity.h b/include/linux/integrity.h
> index 2ea0f2f65ab6..afaae7ad26f4 100644
> --- a/include/linux/integrity.h
> +++ b/include/linux/integrity.h
> @@ -21,38 +21,12 @@ enum integrity_status {
>  
>  /* List of EVM protected security xattrs */
>  #ifdef CONFIG_INTEGRITY
> -extern struct integrity_iint_cache *integrity_inode_get(struct inode *inode);
> -extern void integrity_inode_free(struct inode *inode);
>  extern void __init integrity_load_keys(void);
>  
>  #else
> -static inline struct integrity_iint_cache *
> -				integrity_inode_get(struct inode *inode)
> -{
> -	return NULL;
> -}
> -
> -static inline void integrity_inode_free(struct inode *inode)
> -{
> -	return;
> -}
> -
>  static inline void integrity_load_keys(void)
>  {
>  }
>  #endif /* CONFIG_INTEGRITY */
>  
> -#ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
> -
> -extern int integrity_kernel_module_request(char *kmod_name);
> -
> -#else
> -
> -static inline int integrity_kernel_module_request(char *kmod_name)
> -{
> -	return 0;
> -}
> -
> -#endif /* CONFIG_INTEGRITY_ASYMMETRIC_KEYS */
> -
>  #endif /* _LINUX_INTEGRITY_H */
> diff --git a/security/integrity/iint.c b/security/integrity/iint.c
> index 0b0ac71142e8..882fde2a2607 100644
> --- a/security/integrity/iint.c
> +++ b/security/integrity/iint.c
> @@ -171,7 +171,7 @@ struct integrity_iint_cache *integrity_inode_get(struct inode *inode)
>   *
>   * Free the integrity information(iint) associated with an inode.
>   */
> -void integrity_inode_free(struct inode *inode)
> +static void integrity_inode_free(struct inode *inode)
>  {
>  	struct integrity_iint_cache *iint;
>  
> @@ -193,11 +193,39 @@ static void iint_init_once(void *foo)
>  	memset(iint, 0, sizeof(*iint));
>  }
>  
> +static struct security_hook_list integrity_hooks[] __ro_after_init = {
> +	LSM_HOOK_INIT(inode_free_security, integrity_inode_free),
> +#ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
> +	LSM_HOOK_INIT(kernel_module_request, integrity_kernel_module_request),
> +#endif
> +};
> +
> +/*
> + * Perform the initialization of the 'integrity', 'ima' and 'evm' LSMs to
> + * ensure that the management of integrity metadata is working at the time
> + * IMA and EVM hooks are registered to the LSM infrastructure, and to keep
> + * the original ordering of IMA and EVM functions as when they were hardcoded.
> + */
>  static int __init integrity_lsm_init(void)
>  {
> +	const struct lsm_id *lsmid;
> +
>  	iint_cache =
>  	    kmem_cache_create("iint_cache", sizeof(struct integrity_iint_cache),
>  			      0, SLAB_PANIC, iint_init_once);
> +	/*
> +	 * Obtain either the IMA or EVM LSM ID to register integrity-specific
> +	 * hooks under that LSM, since there is no LSM ID assigned to the
> +	 * 'integrity' LSM.
> +	 */
> +	lsmid = ima_get_lsm_id();
> +	if (!lsmid)
> +		lsmid = evm_get_lsm_id();
> +	/* No point in continuing, since both IMA and EVM are disabled. */
> +	if (!lsmid)
> +		return 0;
> +
> +	security_add_hooks(integrity_hooks, ARRAY_SIZE(integrity_hooks), lsmid);
>  	init_ima_lsm();
>  	init_evm_lsm();
>  	return 0;
> diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
> index 7534ec06324e..e4df82d6f6e7 100644
> --- a/security/integrity/integrity.h
> +++ b/security/integrity/integrity.h
> @@ -180,6 +180,7 @@ struct integrity_iint_cache {
>   * integrity data associated with an inode.
>   */
>  struct integrity_iint_cache *integrity_iint_find(struct inode *inode);
> +struct integrity_iint_cache *integrity_inode_get(struct inode *inode);
>  
>  int integrity_kernel_read(struct file *file, loff_t offset,
>  			  void *addr, unsigned long count);
> @@ -266,12 +267,18 @@ static inline int __init integrity_load_cert(const unsigned int id,
>  #ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
>  int asymmetric_verify(struct key *keyring, const char *sig,
>  		      int siglen, const char *data, int datalen);
> +int integrity_kernel_module_request(char *kmod_name);
>  #else
>  static inline int asymmetric_verify(struct key *keyring, const char *sig,
>  				    int siglen, const char *data, int datalen)
>  {
>  	return -EOPNOTSUPP;
>  }
> +
> +static inline int integrity_kernel_module_request(char *kmod_name)
> +{
> +	return 0;
> +}
>  #endif
>  
>  #ifdef CONFIG_IMA_APPRAISE_MODSIG
> diff --git a/security/security.c b/security/security.c
> index 9703549b6ddc..0d9eaa4cd260 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -19,7 +19,6 @@
>  #include <linux/kernel.h>
>  #include <linux/kernel_read_file.h>
>  #include <linux/lsm_hooks.h>
> -#include <linux/integrity.h>
>  #include <linux/fsnotify.h>
>  #include <linux/mman.h>
>  #include <linux/mount.h>
> @@ -1597,7 +1596,6 @@ static void inode_free_by_rcu(struct rcu_head *head)
>   */
>  void security_inode_free(struct inode *inode)
>  {
> -	integrity_inode_free(inode);
>  	call_void_hook(inode_free_security, inode);
>  	/*
>  	 * The inode may still be referenced in a path walk and
> @@ -3182,12 +3180,7 @@ int security_kernel_create_files_as(struct cred *new, struct inode *inode)
>   */
>  int security_kernel_module_request(char *kmod_name)
>  {
> -	int ret;
> -
> -	ret = call_int_hook(kernel_module_request, 0, kmod_name);
> -	if (ret)
> -		return ret;
> -	return integrity_kernel_module_request(kmod_name);
> +	return call_int_hook(kernel_module_request, 0, kmod_name);
>  }
>  
>  /**