linux-kernel - Re: net: atm: Spectre v1 fix introduced bug in bcb964012d1b in -stable

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Date:   Mon, 20 May 2019 18:15:42 +0200
From:   Pavel Machek <pavel@...x.de>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Pavel Machek <pavel@...x.de>, stable@...nel.org,
        kernel list <linux-kernel@...r.kernel.org>,
        gustavo@...eddedor.com, davem@...emloft.net
Subject: Re: net: atm: Spectre v1 fix introduced bug in bcb964012d1b in
 -stable

On Mon 2019-05-20 16:00:07, Greg KH wrote:
> On Mon, May 20, 2019 at 02:40:14PM +0200, Pavel Machek wrote:
> > 
> > In lecd_attach, if arg is < 0, it was treated as 0. Spectre v1 fix
> > changed that. Bug does not exist in mainline AFAICT.
> > 
> > Signed-off-by: Pavel Machek <pavel@...x.de>
> > # for 4.19.y
> > 
> > diff --git a/net/atm/lec.c b/net/atm/lec.c
> > index ad4f829193f0..ed279cd912f4 100644
> > --- a/net/atm/lec.c
> > +++ b/net/atm/lec.c
> > @@ -731,7 +731,7 @@ static int lecd_attach(struct atm_vcc *vcc, int arg)
> >  		i = arg;
> >  	if (arg >= MAX_LEC_ITF)
> >  		return -EINVAL;
> > -	i = array_index_nospec(arg, MAX_LEC_ITF);
> > +	i = array_index_nospec(i, MAX_LEC_ITF);
> >  	if (!dev_lec[i]) {
> >  		int size;
> >  
> 
> Why is this only for 4.19.y?  What is different in Linus's tree that
> makes this not needed there?

Mainline sanitizes "arg", 4.19 copies "arg" into "i" then sanitizes
it. Take a look, it is local to the function.
								Pavel
-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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