linux-kernel - Re: [PATCH] consolemap: Fix a memory leaking bug in drivers/tty/vt/consolemap.c

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Message-ID: <201905221353.AD8E585E6D@keescook>
Date:   Wed, 22 May 2019 13:54:47 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Gen Zhang <blackgod016574@...il.com>
Cc:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] consolemap: Fix a memory leaking bug in
 drivers/tty/vt/consolemap.c

On Wed, May 22, 2019 at 09:50:55AM +0800, Gen Zhang wrote:
> On Tue, May 21, 2019 at 01:44:33PM -0700, Kees Cook wrote:
> > This doesn't look safe to me: p->uni_pgdir[n] will still have a handle
> > to the freed memory, won't it?
> > 
> Thanks for your reply, Kees!
> I think you are right. Maybe we should do this:
> 	kfree(p1);
> 	p->uni_pgdir[n] = NULL;
> Is this correct?

That's what I'm not sure about. I *think* so, from reading the code, but
I'd love to have Greg (or someone more familiar with the code) to
double-check this.

Otherwise, yeah, this looks right. Please send a v2 and we can debate
the correctness there, if it turns out to be wrong. :)

-- 
Kees Cook