linux-kernel - Re: [PATCH] Smack: implement revoking all rules for a subject label

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Message-ID: <502944E2.4070909@schaufler-ca.com>
Date:	Mon, 13 Aug 2012 11:18:10 -0700
From:	Casey Schaufler <casey@...aufler-ca.com>
To:	Rafal Krypa <r.krypa@...sung.com>
CC:	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH] Smack: implement revoking all rules for a subject label

On 7/11/2012 8:49 AM, Rafal Krypa wrote:
> Add /smack/revoke-subject special file. Writing a SMACK label to this file will
> set the access to '-' for all access rules with that subject label.
>
> Targeted for git://git.gitorious.org/smack-next/kernel.git
>
> Signed-off-by: Rafal Krypa <r.krypa@...sung.com>

Applied to git://git.gitorious.org/smack-next/kernel.git


> ---
>  Documentation/security/Smack.txt |    3 ++
>  security/smack/smackfs.c         |   75 ++++++++++++++++++++++++++++++++++++++
>  2 files changed, 78 insertions(+)
>
> diff --git a/Documentation/security/Smack.txt b/Documentation/security/Smack.txt
> index a416479..e68536d 100644
> --- a/Documentation/security/Smack.txt
> +++ b/Documentation/security/Smack.txt
> @@ -194,6 +194,9 @@ onlycap
>  	these capabilities are effective at for processes with any
>  	label. The value is set by writing the desired label to the
>  	file or cleared by writing "-" to the file.
> +revoke-subject
> +	Writing a Smack label here sets the access to '-' for all access
> +	rules with that subject label.
>  
>  You can add access rules in /etc/smack/accesses. They take the form:
>  
> diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
> index d31e6d9..c434441 100644
> --- a/security/smack/smackfs.c
> +++ b/security/smack/smackfs.c
> @@ -49,6 +49,7 @@ enum smk_inos {
>  	SMK_LOAD_SELF2	= 15,	/* load task specific rules with long labels */
>  	SMK_ACCESS2	= 16,	/* make an access check with long labels */
>  	SMK_CIPSO2	= 17,	/* load long label -> CIPSO mapping */
> +	SMK_REVOKE_SUBJ	= 18,	/* set rules with subject label to '-' */
>  };
>  
>  /*
> @@ -1992,6 +1993,77 @@ static const struct file_operations smk_access2_ops = {
>  };
>  
>  /**
> + * smk_write_revoke_subj - write() for /smack/revoke-subject
> + * @file: file pointer
> + * @buf: data from user space
> + * @count: bytes sent
> + * @ppos: where to start - must be 0
> + */
> +static ssize_t smk_write_revoke_subj(struct file *file, const char __user *buf,
> +				size_t count, loff_t *ppos)
> +{
> +	char *data = NULL;
> +	const char *cp = NULL;
> +	struct smack_known *skp;
> +	struct smack_rule *sp;
> +	struct list_head *rule_list;
> +	struct mutex *rule_lock;
> +	int rc = count;
> +
> +	if (*ppos != 0)
> +		return -EINVAL;
> +
> +	if (!smack_privileged(CAP_MAC_ADMIN))
> +		return -EPERM;
> +
> +	if (count == 0 || count > SMK_LONGLABEL)
> +		return -EINVAL;
> +
> +	data = kzalloc(count, GFP_KERNEL);
> +	if (data == NULL)
> +		return -ENOMEM;
> +
> +	if (copy_from_user(data, buf, count) != 0) {
> +		rc = -EFAULT;
> +		goto free_out;
> +	}
> +
> +	cp = smk_parse_smack(data, count);
> +	if (cp == NULL) {
> +		rc = -EINVAL;
> +		goto free_out;
> +	}
> +
> +	skp = smk_find_entry(cp);
> +	if (skp == NULL) {
> +		rc = -EINVAL;
> +		goto free_out;
> +	}
> +
> +	rule_list = &skp->smk_rules;
> +	rule_lock = &skp->smk_rules_lock;
> +
> +	mutex_lock(rule_lock);
> +
> +	list_for_each_entry_rcu(sp, rule_list, list)
> +		sp->smk_access = 0;
> +
> +	mutex_unlock(rule_lock);
> +
> +free_out:
> +	kfree(data);
> +	kfree(cp);
> +	return rc;
> +}
> +
> +static const struct file_operations smk_revoke_subj_ops = {
> +	.write		= smk_write_revoke_subj,
> +	.read		= simple_transaction_read,
> +	.release	= simple_transaction_release,
> +	.llseek		= generic_file_llseek,
> +};
> +
> +/**
>   * smk_fill_super - fill the /smackfs superblock
>   * @sb: the empty superblock
>   * @data: unused
> @@ -2037,6 +2109,9 @@ static int smk_fill_super(struct super_block *sb, void *data, int silent)
>  			"access2", &smk_access2_ops, S_IRUGO|S_IWUGO},
>  		[SMK_CIPSO2] = {
>  			"cipso2", &smk_cipso2_ops, S_IRUGO|S_IWUSR},
> +		[SMK_REVOKE_SUBJ] = {
> +			"revoke-subject", &smk_revoke_subj_ops,
> +			S_IRUGO|S_IWUSR},
>  		/* last one */
>  			{""}
>  	};

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