linux-kernel - Re: [PATCH v5 09/11] PM: hibernate: Mix user key in encrypted hibernate

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Message-ID: <Y3GBTCwcRcI0oGQO@sol.localdomain>
Date:   Sun, 13 Nov 2022 15:44:12 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Evan Green <evgreen@...omium.org>
Cc:     linux-kernel@...r.kernel.org, corbet@....net,
        linux-integrity@...r.kernel.org, gwendal@...omium.org,
        dianders@...omium.org, apronin@...omium.org,
        Pavel Machek <pavel@....cz>, Ben Boeckel <me@...boeckel.net>,
        rjw@...ysocki.net, jejb@...ux.ibm.com,
        Kees Cook <keescook@...omium.org>, dlunev@...gle.com,
        zohar@...ux.ibm.com, Matthew Garrett <mgarrett@...ora.tech>,
        jarkko@...nel.org, linux-pm@...r.kernel.org,
        Len Brown <len.brown@...el.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH v5 09/11] PM: hibernate: Mix user key in encrypted
 hibernate

On Fri, Nov 11, 2022 at 03:16:34PM -0800, Evan Green wrote:
> Limiting this to the data portion allows the kernel to receive the page
> map and prepare its giant allocation even if this user key is not yet
> available (ie the user has not yet finished typing in their password).

What is meant by the "data portion"?

> +int snapshot_set_user_key(struct snapshot_data *data,
> +	struct uswsusp_user_key __user *key)
> +{
> +	struct uswsusp_user_key user_key;
> +	unsigned int key_len;
> +	int rc;
> +	loff_t size;
> +
> +	/*
> +	 * Return the metadata size, the number of bytes that can be fed in before
> +	 * the user data key is needed at resume time.
> +	 */
> +	size = snapshot_get_meta_data_size();
> +	rc = put_user(size, &key->meta_size);
> +	if (rc)
> +		return rc;
> +
> +	rc = copy_from_user(&user_key, key, sizeof(struct uswsusp_user_key));
> +	if (rc)
> +		return rc;

This isn't correctly checking the return value of copy_from_user().

> +
> +	BUILD_BUG_ON(sizeof(data->user_key) < sizeof(user_key.key));
> +
> +	key_len = min_t(__u32, user_key.key_len, sizeof(data->user_key));
> +	if (key_len < 8)
> +		return -EINVAL;

Shouldn't -EINVAL also be returned if key_len is too large?

- Eric