linux-kernel - Re: [PATCH v2] consolemap: Fix a memory leaking bug in drivers/tty/vt/consolemap.c

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Date:   Fri, 24 May 2019 10:14:22 +0800
From:   Gen Zhang <blackgod016574@...il.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] consolemap: Fix a memory leaking bug in
 drivers/tty/vt/consolemap.c

On Thu, May 23, 2019 at 09:54:18AM -0700, Kees Cook wrote:
> On Thu, May 23, 2019 at 08:34:52AM +0800, Gen Zhang wrote:
> > In function con_insert_unipair(), when allocation for p2 and p1[n]
> > fails, ENOMEM is returned, but previously allocated p1 is not freed, 
> > remains as leaking memory. Thus we should free p1 as well when this
> > allocation fails.
> > 
> > Signed-off-by: Gen Zhang <blackgod016574@...il.com>
> 
> As far as I can see this is correct, as it's just restoring the prior
> state before the p1 allocation.
> 
> Reviewed-by: Kees Cook <keescook@...omium.org>
> 
Thanks for your review, Kees!

Thanks
Gen
> > ---
> > diff --git a/drivers/tty/vt/consolemap.c b/drivers/tty/vt/consolemap.c
> > index b28aa0d..79fcc96 100644
> > --- a/drivers/tty/vt/consolemap.c
> > +++ b/drivers/tty/vt/consolemap.c
> > @@ -489,7 +489,11 @@ con_insert_unipair(struct uni_pagedir *p, u_short unicode, u_short fontpos)
> >  	p2 = p1[n = (unicode >> 6) & 0x1f];
> >  	if (!p2) {
> >  		p2 = p1[n] = kmalloc_array(64, sizeof(u16), GFP_KERNEL);
> > -		if (!p2) return -ENOMEM;
> > +		if (!p2) {
> > +			kfree(p1);
> > +			p->uni_pgdir[n] = NULL;
> > +			return -ENOMEM;
> > +		}
> >  		memset(p2, 0xff, 64*sizeof(u16)); /* No glyphs for the characters (yet) */
> >  	}
> >  
> > ---
> 
> -- 
> Kees Cook