linux-kernel - Re: TIOCGWINSZ retuns old pty size after receiving SIGWINCH

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: <20080819004026.2dac3ba6.akpm@linux-foundation.org>
Date:	Tue, 19 Aug 2008 00:40:26 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Ico Doornekamp <lkml@...v.nl>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: TIOCGWINSZ retuns old pty size after receiving SIGWINCH

On Sun, 10 Aug 2008 17:08:59 +0200 Ico Doornekamp <lkml@...v.nl> wrote:

> 
> Hello,
> 
> Recently my X terminals showed annoying behaviour where the application
> in the terminal was not resized properly to the actual size of the X
> terminal emulator window, resulting in a lot of misaligned text on the
> screen. Hunting the issue down from the windowmanager and the terminal
> emulator program, I suspect the problem might lie in the kernel. I'm
> running 2.6.26 on a dual core i386.
> 
> What I see is this: the userspace application receives a SIGWINCH signal
> and acquires the terminal size usign the TIOCGWINSZ ioctl. It seems that
> in some cases the old instead of the new terminal size is returned.
> A small delay before the ioctl seems to 'fix' this behaviour.
> 
> I noticed some changes involving locking in the the pty code in the last
> kernel verions, could one of these changes cause the above behaviour ? If
> so, wouldn't this affect much more users ?
> 

hm, that code is pretty simple and although it does the SIGWINCH and
the window-size setting in a peculiar order, it looks to be race-free.

Approximately what proportion of the time does it go wrong?
--
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/