linux-kernel - Re: [PATCH v2 1/3] seccomp: Add find

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Date:   Thu, 28 May 2020 23:23:32 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Sargun Dhillon <sargun@...gun.me>
Cc:     christian.brauner@...ntu.com,
        containers@...ts.linux-foundation.org, cyphar@...har.com,
        jannh@...gle.com, jeffv@...gle.com, linux-api@...r.kernel.org,
        linux-kernel@...r.kernel.org, palmer@...gle.com, rsesek@...gle.com,
        tycho@...ho.ws, Matt Denton <mpdenton@...gle.com>
Subject: Re: [PATCH v2 1/3] seccomp: Add find_notification helper

On Thu, May 28, 2020 at 04:08:56AM -0700, Sargun Dhillon wrote:
> This adds a helper which can iterate through a seccomp_filter to
> find a notification matching an ID. It removes several replicated
> chunks of code.

Nice, yes. I was noticing this redundancy too while I was looking at
notify locking earlier today. One note below...

> +/* must be called with notif_lock held */
> +static inline struct seccomp_knotif *
> +find_notification(struct seccomp_filter *filter, u64 id)
> +{
> +	struct seccomp_knotif *cur;

While the comment is good, let's actually enforce this with:

if (WARN_ON(!mutex_is_locked(&filter->notif_lock)))
	return NULL;

> +
> +	list_for_each_entry(cur, &filter->notif->notifications, list) {
> +		if (cur->id == id)
> +			return cur;
> +	}
> +
> +	return NULL;
> +}

Everything else looks good!

-- 
Kees Cook