linux-kernel - Re: [PATCH] kref: Avoid null pointer dereference after WARN

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Message-ID: <20170627110013.GA3026@zx2c4.com>
Date:   Tue, 27 Jun 2017 13:00:16 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Kees Cook <keescook@...omium.org>, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Daniel Micay <danielmicay@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kref: Avoid null pointer dereference after WARN

On Tue, Jun 27, 2017 at 09:06:26AM +0200, Greg Kroah-Hartman wrote:
> I remember one complaint was that WARN_ON was "huge" and this bloated
> the kernel code a lot.  But then that got fixed up.  Is BUG_ON going to
> cause the same complaint again?

Complaint or not, I'm pretty sure using BUG_ON here is the right
behavior. If removing it will result in a null pointer dereference (and
subsequent function call), that's bad news bears, especially on systems
with a zero mmap_min_addr or combined with other bugs.

If somehow a driver manages to pass a NULL as the release function,
something is really messed up and the kernel should "safely" panic
instead.

> 
> thanks,
> 
> greg k-h

-- 
Jason A. Donenfeld
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