linux-kernel - Re: [PATCH v6 1/3] LSM: Add /sys/kernel/security/lsm

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Message-Id: <201611012153.IHJ52634.OSOLMFFOFVQJtH@I-love.SAKURA.ne.jp>
Date:   Tue, 1 Nov 2016 21:53:09 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     casey@...aufler-ca.com, linux-security-module@...r.kernel.org,
        jmorris@...ei.org
Cc:     john.johansen@...onical.com, paul@...l-moore.com,
        keescook@...omium.org, sds@...ho.nsa.gov,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 1/3] LSM: Add /sys/kernel/security/lsm

Casey Schaufler wrote:
> diff --git a/security/security.c b/security/security.c
> index f825304..f0a802ee 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -32,6 +32,7 @@
>  /* Maximum number of letters for an LSM name string */
>  #define SECURITY_NAME_MAX	10
>  
> +char *lsm_names;
>  /* Boot-time LSM user choice */
>  static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
>  	CONFIG_DEFAULT_SECURITY;
> @@ -78,6 +79,22 @@ static int __init choose_lsm(char *str)
>  }
>  __setup("security=", choose_lsm);
>  
> +static int lsm_append(char *new, char **result)
> +{
> +	char *cp;
> +
> +	if (*result == NULL) {
> +		*result = kstrdup(new, GFP_KERNEL);
> +	} else {
> +		cp = kasprintf(GFP_KERNEL, "%s,%s", *result, new);
> +		if (cp == NULL)
> +			return -ENOMEM;
> +		kfree(*result);
> +		*result = cp;
> +	}
> +	return 0;
> +}
> +

I didn't check past discussion, but how do you handle security_delete_hooks()
case (I mean, "selinux" will remain there when reading /sys/kernel/security/lsm
even after it is disabled at runtime)? I think holding module name as one of
"union security_list_options" members will avoid memory allocation handling
and simplify things.