netdev - Re: [PATCH] netlink: add policy attribute range validation

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Message-ID: <1537993482.28767.34.camel@sipsolutions.net>
Date:   Wed, 26 Sep 2018 22:24:42 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] netlink: add policy attribute range validation

Another thing to note:

Given the union of validation_data pointer and min/max, we'll always get
into this:

> +	/* validate range */
> +	if (pt->min || pt->max) {

if validation_data is set, but of course end up taking the default case,
where nothing further happens:

> +		default:
> +			/* no further validation */
> +			validate = false;
> +			break;
> +		}
> +
> +		if (validate && (value < pt->min || value > pt->max)) {
> +			NL_SET_ERR_MSG_ATTR(extack, nla,
> +					    "integer out of range");
> +			return -ERANGE;
> +		}
> +	}
> +
>  	return 0;

I'm not *entirely* happy with this, but I haven't been able to come up
with a way that doesn't do this, doesn't duplicate the nla types list
(NLA_{U,S}{8,16,32,64}) in the code, and also loads the attribute value
only if validation is needed.

johannes