From: Pavel Machek <pavel@denx.de>
To: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
Pavel Machek <pavel@denx.de>,
stable@kernel.org, kernel list <linux-kernel@vger.kernel.org>,
davem@davemloft.net
Subject: Re: net: atm: Spectre v1 fix introduced bug in bcb964012d1b in -stable
Date: Mon, 20 May 2019 23:00:12 +0200 [thread overview]
Message-ID: <20190520210012.GA18021@amd> (raw)
In-Reply-To: <101e123e-9dfa-7c98-b182-e4ef277560f9@embeddedor.com>
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On Mon 2019-05-20 09:26:45, Gustavo A. R. Silva wrote:
>
>
> On 5/20/19 9:00 AM, 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@denx.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?
> >
>
> The only difference is this clean up:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fdd1a8103a6df50bdeacd8bb04c3f6976cb9ae41
>
> As Dan says, the code works fine, but the *i* value wasn't being used
> anymore, so that piece of code was a bit confusing.
Yep, you are right, code managed to confused me: array_index_nospec
really returns 0 if it is out of bounds,
(typeof(_i)) (_i & _mask);
because _mask is always 0 or ~0.
Best regards,
Pavel
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
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next prev parent reply other threads:[~2019-05-20 21:00 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-20 12:40 net: atm: Spectre v1 fix introduced bug in bcb964012d1b in -stable Pavel Machek
2019-05-20 14:00 ` Greg KH
2019-05-20 14:26 ` Gustavo A. R. Silva
2019-05-20 21:00 ` Pavel Machek [this message]
2019-05-20 16:15 ` Pavel Machek
2019-05-20 14:15 ` Gustavo A. R. Silva
2019-05-20 16:15 ` Pavel Machek
2019-05-20 16:54 ` Gustavo A. R. Silva
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