linux-kernel - Re: [PATCH 2/2] tty: rework pty count limiting

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: <4F022DFA.1090105@openvz.org>
Date:	Tue, 03 Jan 2012 02:21:46 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	Greg KH <gregkh@...e.de>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] tty: rework pty count limiting

Greg KH wrote:
> On Mon, Jan 02, 2012 at 09:23:01PM +0400, Konstantin Khlebnikov wrote:
>> After adding devpts multiple-insrances sysctl kernel.pty.max limit pty count for
>> each devpts instance independently, while kernel.pty.nr shows total pty count.
>>
>> This patch restores sysctl kernel.pty.max as global limit (4096 by default),
>> adds pty reseve for main devpts (mounted without "newinstance" argument),
>> and new sysctl to tune it: kernel.pty.reserve (1024 by default)
>>
>> Also it adds devpts mount option "max=%d" to limit pty count for each devpts
>> instance independently. (by default NR_UNIX98_PTY_MAX == 2^20)
>>
>> Thus devpts instances in containers cannot eat up all available pty even if we didn't
>> set any limits, while with "max" argument we can adjust limits more precisely.
>>
>> Plus, now open("/dev/ptmx") return -ENOSPC in case lack of pty indexes,
>> this is more informative than -EIO.
>
> That's a userspace api change, why is this going to be allowed?

open() can return -ENOSPC in case normal fs,
meanwhile error codes for /dev/ptmx wasn't documented at all:
there is nothing in manpage pts, pty and ptmx.
manpage posix_openpt and getpt refers to manpage open(2).
I can return EIO back, if this is critical.

>
> greg k-h
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/