Re: [PATCH 1/6] selinux: do not allocate ancillary buffer on first load

[Stephen Smalley <sds@tycho.nsa.gov>]

On 1/16/20 7:04 AM, Ondrej Mosnacek wrote:
> In security_load_policy(), we can defer allocating the newpolicydb
> ancillary array to after checking state->initialized, thereby avoiding
> the pointless allocation when loading policy the first time.
> 
> Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>

Reviewed-by: Stephen Smalley <sds@tycho.nsa.gov>

> ---
>   security/selinux/ss/services.c | 28 +++++++++++++---------------
>   1 file changed, 13 insertions(+), 15 deletions(-)
> 
> diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
> index 55cf42945cba..42ca9f6dbbf4 100644
> --- a/security/selinux/ss/services.c
> +++ b/security/selinux/ss/services.c
> @@ -2183,26 +2183,17 @@ int security_load_policy(struct selinux_state *state, void *data, size_t len)
>   	int rc = 0;
>   	struct policy_file file = { data, len }, *fp = &file;
>   
> -	oldpolicydb = kcalloc(2, sizeof(*oldpolicydb), GFP_KERNEL);
> -	if (!oldpolicydb) {
> -		rc = -ENOMEM;
> -		goto out;
> -	}
> -	newpolicydb = oldpolicydb + 1;
> -
>   	policydb = &state->ss->policydb;
>   
>   	newsidtab = kmalloc(sizeof(*newsidtab), GFP_KERNEL);
> -	if (!newsidtab) {
> -		rc = -ENOMEM;
> -		goto out;
> -	}
> +	if (!newsidtab)
> +		return -ENOMEM;
>   
>   	if (!state->initialized) {
>   		rc = policydb_read(policydb, fp);
>   		if (rc) {
>   			kfree(newsidtab);
> -			goto out;
> +			return rc;
>   		}
>   
>   		policydb->len = len;
> @@ -2211,14 +2202,14 @@ int security_load_policy(struct selinux_state *state, void *data, size_t len)
>   		if (rc) {
>   			kfree(newsidtab);
>   			policydb_destroy(policydb);
> -			goto out;
> +			return rc;
>   		}
>   
>   		rc = policydb_load_isids(policydb, newsidtab);
>   		if (rc) {
>   			kfree(newsidtab);
>   			policydb_destroy(policydb);
> -			goto out;
> +			return rc;
>   		}
>   
>   		state->ss->sidtab = newsidtab;
> @@ -2231,9 +2222,16 @@ int security_load_policy(struct selinux_state *state, void *data, size_t len)
>   		selinux_status_update_policyload(state, seqno);
>   		selinux_netlbl_cache_invalidate();
>   		selinux_xfrm_notify_policyload();
> -		goto out;
> +		return 0;
>   	}
>   
> +	oldpolicydb = kcalloc(2, sizeof(*oldpolicydb), GFP_KERNEL);
> +	if (!oldpolicydb) {
> +		kfree(newsidtab);
> +		return -ENOMEM;
> +	}
> +	newpolicydb = oldpolicydb + 1;
> +
>   	rc = policydb_read(newpolicydb, fp);
>   	if (rc) {
>   		kfree(newsidtab);
>