linux-kernel - Re: [PATCH 6/7] fcntl: Don't use ambiguous SIG_POLL si

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87lgni7c33.fsf@xmission.com>
Date:   Thu, 20 Jul 2017 21:33:52 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andrei Vagin <avagin@...tuozzo.com>,
        Thomas Gleixner <tglx@...utronix.de>, Greg KH <greg@...ah.com>,
        Andrey Vagin <avagin@...nvz.org>,
        Serge Hallyn <serge@...lyn.com>,
        Pavel Emelyanov <xemul@...tuozzo.com>,
        Cyrill Gorcunov <gorcunov@...nvz.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Willy Tarreau <w@....eu>, linux-arch@...r.kernel.org,
        linux-api@...r.kernel.org,
        Linux Containers <containers@...ts.linux-foundation.org>,
        Michael Kerrisk <mtk.manpages@...il.com>
Subject: Re: [PATCH 6/7] fcntl: Don't use ambiguous SIG_POLL si_codes



Oleg Nesterov <oleg@...hat.com> writes:

> On 07/18, Eric W. Biederman wrote:
>>
>> -			BUG_ON((reason & __SI_MASK) != __SI_POLL);
>> +			BUG_ON((reason < POLL_IN) || (reason > NSIGPOLL));
>                                                       ^^^^^^^^^^^^^^^^^
> looks obviously wrong? Say, POLL_IN is obviously > NSIGPOLL == 6.

Strictly speaking that code is wrong until the next patch
when I remove __SI_POLL.  That is my mistake.

When the values are not their messed up internal kernel variants
the code works fine and makes sense.

#define POLL_IN		1	/* data input available */
#define POLL_OUT	2	/* output buffers available */
#define POLL_MSG	3	/* input message available */
#define POLL_ERR	4	/* i/o error */
#define POLL_PRI	5	/* high priority input available */
#define POLL_HUP	6	/* device disconnected */
#define NSIGPOLL	6

> Probably you meant
>
> 			BUG_ON((reason < POLL_IN) || (reason - POLL_IN > NSIGPOLL)
>
> ?
>
> but this contradicts with the next line:

>>  			if (reason - POLL_IN >= NSIGPOLL)
>>  				si.si_band  = ~0L;
>
> confused...

I am mystified why we test for a condition that we have been bugging on
for ages.

Eric