[PATCH] devpts_get_tty() should validate inode

[Greg KH]

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 at us.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