linux-kernel - Re: [PATCH v9 21/23] ima: Introduce securityfs file to activate an IMA namespace

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Date:   Thu, 27 Jan 2022 10:24:14 -0500
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     Christian Brauner <brauner@...nel.org>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>
Cc:     linux-integrity@...r.kernel.org, zohar@...ux.ibm.com,
        serge@...lyn.com, christian.brauner@...ntu.com,
        containers@...ts.linux.dev, dmitry.kasatkin@...il.com,
        ebiederm@...ssion.com, krzysztof.struczynski@...wei.com,
        roberto.sassu@...wei.com, mpeters@...hat.com, lhinds@...hat.com,
        lsturman@...hat.com, puiterwi@...hat.com, jejb@...ux.ibm.com,
        jamjoom@...ibm.com, linux-kernel@...r.kernel.org,
        paul@...l-moore.com, rgb@...hat.com,
        linux-security-module@...r.kernel.org, jmorris@...ei.org
Subject: Re: [PATCH v9 21/23] ima: Introduce securityfs file to activate an
 IMA namespace


On 1/26/22 09:31, Christian Brauner wrote:
> On Tue, Jan 25, 2022 at 05:46:43PM -0500, Stefan Berger wrote:
>
> Hm, I'd rather do something like (uncompiled, untested):
>
> +static ssize_t ima_write_active(struct file *filp,
> 				const char __user *buf,
> 				size_t count, loff_t *ppos)
> {
> 	struct ima_namespace *ns = &init_ima_ns;
> 	int err;
> 	unsigned int active;
> 	char *kbuf = NULL;
> 	ssize_t length;
>
> 	if (count >= 3)
> 		return -EINVAL;
>
> 	/* No partial writes. */
> 	if (*ppos != 0)
> 		return -EINVAL;
>
> 	if (ns_active(ns))
> 		return -EBUSY;
>
> 	kbuf = memdup_user_nul(buf, count);
> 	if (IS_ERR(kbuf))
> 		return PTR_ERR(kbuf);
>
> 	err = kstrtouint(kbuf, 10, &active);
> 	kfree(kbuf);
> 	if (err)
> 		return err;
>
> 	if (active != 1)
> 		return -EINVAL;
>
> 	atomic_set(&ns->active, 1);
> 	return count;
> }

Rearranged it to look lik this?

static ssize_t ima_write_active(struct file *filp,
                                 const char __user *buf,
                                 size_t count, loff_t *ppos)
{
         struct ima_namespace *ns = &init_ima_ns;
         unsigned int active;
         char *kbuf;
         int err;

         if (ns_is_active(ns))
                 return -EBUSY;

         /* accepting '1\n' and '1\0' and no partial writes */
         if (count >= 3 || *ppos != 0)
                 return -EINVAL;

         kbuf = memdup_user_nul(buf, count);
         if (IS_ERR(kbuf))
                 return PTR_ERR(kbuf);

         err = kstrtouint(kbuf, 10, &active);
         kfree(kbuf);
         if (err)
                 return err;

         if (active != 1)
                 return -EINVAL;

         atomic_set(&ns->active, 1);
         return count;
}