linux-kernel - Re: [PATCH 4.14 17/89] futex: Prevent overflow by strengthen input validation

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Date:   Thu, 25 Jan 2018 15:30:36 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Jiri Slaby <jslaby@...e.cz>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Li Jinyue <lijinyue@...wei.com>, peterz@...radead.org,
        dvhart@...radead.org
Subject: Re: [PATCH 4.14 17/89] futex: Prevent overflow by strengthen input
 validation

On Thu, 25 Jan 2018, Jiri Slaby wrote:

> On 01/25/2018, 03:03 PM, Thomas Gleixner wrote:
> > On Thu, 25 Jan 2018, Jiri Slaby wrote:
> >> On 01/22/2018, 09:44 AM, Greg Kroah-Hartman wrote:
> >>> +	if (nr_wake < 0 || nr_requeue < 0)
> >>> +		return -EINVAL;
> >>
> >> This breaks strace's test suite on 4.14.15 (and is present in upstream
> >> obviously too):
> >>     futex(0x7ff568b44ffc, 0x3, 0xfacefeed, 0xbadda7a0ca7b100d,
> >> 0x7ff568b44ffc, 0x9caffee1) = -1: Invalid argument
> > 
> > And why the hell is strace expecting this to be valid?
> 
> You ought to ask somebody else, I was confused the very same way:
> 
> My FIX:
> https://github.com/strace/strace/pull/16/commits/777587ea509481666274df88671949b390f05cc3
> 
> Their NACK:
> https://github.com/strace/strace/pull/16#issuecomment-341614984

https://github.com/strace/strace/commit/79d10dfc20985225e4ea044d3875c4cea09053d7

 Update futex test in accordance with kernel's v4.15-rc7-202-gfbe0e83

* futex.c (VALP, VALP_PR, VAL2P, VAL2P_PR): New macro definitions.
(main): Allow EINVAL on *REQUEUE* checks with VAL/VAL2 with higher bit
being set, check that the existing behaviour preserved with VALP/VAL2P
where higher bit is unset.

So what's the problem?

Thanks,

	tglx