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

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Message-ID: <20200529174037.GA11153@ircssh-2.c.rugged-nimbus-611.internal>
Date:   Fri, 29 May 2020 17:40:38 +0000
From:   Sargun Dhillon <sargun@...gun.me>
To:     Kees Cook <keescook@...omium.org>
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

> 
> While the comment is good, let's actually enforce this with:
> 
> if (WARN_ON(!mutex_is_locked(&filter->notif_lock)))
> 	return NULL;
> 
I don't see much use of lockdep in seccomp (well, any), but
wouldn't a stronger statement be to use lockdep, and just have:

lockdep_assert_held(&filter->notify_lock);

As that checks that the lock is held by the current task.
Although, that does put this check behind lockdep, which means
that running in "normal" circumstances is less safe (but faster?).