[PATCH v12 04/25] LSM: Use lsmblob in security_kernel_act_as

[Stephen Smalley]

On 12/16/19 5:36 PM, Casey Schaufler wrote:
> Change the security_kernel_act_as interface to use a lsmblob
> structure in place of the single u32 secid in support of
> module stacking. Change its only caller, set_security_override,
> to do the same. Change that one's only caller,
> set_security_override_from_ctx, to call it with the new
> parameter type.
> 
> Reviewed-by: Kees Cook <keescook at chromium.org>
> Reviewed-by: John Johansen <john.johansen at canonical.com>
> Signed-off-by: Casey Schaufler <casey at schaufler-ca.com>

Same question re the WARN_ON, but otherwise:

Acked-by: Stephen Smalley <sds at tycho.nsa.gov>

> ---
>   include/linux/cred.h     |  3 ++-
>   include/linux/security.h |  5 +++--
>   kernel/cred.c            | 10 ++++++----
>   security/security.c      | 14 ++++++++++++--
>   4 files changed, 23 insertions(+), 9 deletions(-)
> 
> diff --git a/include/linux/cred.h b/include/linux/cred.h
> index 18639c069263..03ae0182cba6 100644
> --- a/include/linux/cred.h
> +++ b/include/linux/cred.h
> @@ -18,6 +18,7 @@
>   
>   struct cred;
>   struct inode;
> +struct lsmblob;
>   
>   /*
>    * COW Supplementary groups list
> @@ -165,7 +166,7 @@ extern const struct cred *override_creds(const struct cred *);
>   extern void revert_creds(const struct cred *);
>   extern struct cred *prepare_kernel_cred(struct task_struct *);
>   extern int change_create_files_as(struct cred *, struct inode *);
> -extern int set_security_override(struct cred *, u32);
> +extern int set_security_override(struct cred *, struct lsmblob *);
>   extern int set_security_override_from_ctx(struct cred *, const char *);
>   extern int set_create_files_as(struct cred *, struct inode *);
>   extern int cred_fscmp(const struct cred *, const struct cred *);
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 9c6dbe248eaf..322ed9622819 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -437,7 +437,7 @@ void security_cred_free(struct cred *cred);
>   int security_prepare_creds(struct cred *new, const struct cred *old, gfp_t gfp);
>   void security_transfer_creds(struct cred *new, const struct cred *old);
>   void security_cred_getsecid(const struct cred *c, u32 *secid);
> -int security_kernel_act_as(struct cred *new, u32 secid);
> +int security_kernel_act_as(struct cred *new, struct lsmblob *blob);
>   int security_kernel_create_files_as(struct cred *new, struct inode *inode);
>   int security_kernel_module_request(char *kmod_name);
>   int security_kernel_load_data(enum kernel_load_data_id id);
> @@ -1043,7 +1043,8 @@ static inline void security_transfer_creds(struct cred *new,
>   {
>   }
>   
> -static inline int security_kernel_act_as(struct cred *cred, u32 secid)
> +static inline int security_kernel_act_as(struct cred *cred,
> +					 struct lsmblob *blob)
>   {
>   	return 0;
>   }
> diff --git a/kernel/cred.c b/kernel/cred.c
> index c0a4c12d38b2..846ac4b23c16 100644
> --- a/kernel/cred.c
> +++ b/kernel/cred.c
> @@ -732,14 +732,14 @@ EXPORT_SYMBOL(prepare_kernel_cred);
>   /**
>    * set_security_override - Set the security ID in a set of credentials
>    * @new: The credentials to alter
> - * @secid: The LSM security ID to set
> + * @blob: The LSM security information to set
>    *
>    * Set the LSM security ID in a set of credentials so that the subjective
>    * security is overridden when an alternative set of credentials is used.
>    */
> -int set_security_override(struct cred *new, u32 secid)
> +int set_security_override(struct cred *new, struct lsmblob *blob)
>   {
> -	return security_kernel_act_as(new, secid);
> +	return security_kernel_act_as(new, blob);
>   }
>   EXPORT_SYMBOL(set_security_override);
>   
> @@ -755,6 +755,7 @@ EXPORT_SYMBOL(set_security_override);
>    */
>   int set_security_override_from_ctx(struct cred *new, const char *secctx)
>   {
> +	struct lsmblob blob;
>   	u32 secid;
>   	int ret;
>   
> @@ -762,7 +763,8 @@ int set_security_override_from_ctx(struct cred *new, const char *secctx)
>   	if (ret < 0)
>   		return ret;
>   
> -	return set_security_override(new, secid);
> +	lsmblob_init(&blob, secid);
> +	return set_security_override(new, &blob);
>   }
>   EXPORT_SYMBOL(set_security_override_from_ctx);
>   
> diff --git a/security/security.c b/security/security.c
> index bfea9739c084..cee032b5ce29 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1615,9 +1615,19 @@ void security_cred_getsecid(const struct cred *c, u32 *secid)
>   }
>   EXPORT_SYMBOL(security_cred_getsecid);
>   
> -int security_kernel_act_as(struct cred *new, u32 secid)
> +int security_kernel_act_as(struct cred *new, struct lsmblob *blob)
>   {
> -	return call_int_hook(kernel_act_as, 0, new, secid);
> +	struct security_hook_list *hp;
> +	int rc;
> +
> +	hlist_for_each_entry(hp, &security_hook_heads.kernel_act_as, list) {
> +		if (WARN_ON(hp->lsmid->slot < 0 || hp->lsmid->slot >= lsm_slot))
> +			continue;
> +		rc = hp->hook.kernel_act_as(new, blob->secid[hp->lsmid->slot]);
> +		if (rc != 0)
> +			return rc;
> +	}
> +	return 0;
>   }
>   
>   int security_kernel_create_files_as(struct cred *new, struct inode *inode)
>