linux-kernel - Re: [PATCH] devpts_get_tty() should validate inode

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Message-ID: <20091118034450.GB17349@suse.de>
Date:	Tue, 17 Nov 2009 19:44:50 -0800
From:	Greg KH <gregkh@...e.de>
To:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, hpa@...or.com,
	root@...aldomain.pl,
	Containers <containers@...ts.linux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] devpts_get_tty() should validate inode

On Tue, Nov 17, 2009 at 06:35:43PM -0800, Sukadev Bhattiprolu wrote:
> 
> devpts_get_tty() assumes that the inode passed in is associated with a valid
> pty.  But if the only reference to the pty is via a bind-mount, the inode
> passed to devpts_get_tty() while valid, would refer to a pty that no longer
> exists.
> 
> With a lot of debug effort, Grzegorz Nosek developed a small program (see
> below) to reproduce a crash on recent kernels. This crash is a regression
> introduced by the commit:
> 
> 	commit 527b3e4773628b30d03323a2cb5fb0d84441990f
> 	Author: Sukadev Bhattiprolu <sukadev@...ibm.com>
> 	Date:   Mon Oct 13 10:43:08 2008 +0100
> 
> To fix, ensure that the dentry associated with the inode has not yet been
> deleted/unhashed by devpts_pty_kill().
> 
> See also:
> https://lists.linux-foundation.org/pipermail/containers/2009-July/019273.html 

Good debugging, I'll queue this up.

greg k-h
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