linux-kernel - Bisected regression: iterate_fd() selinux change affects flash plugin

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Message-ID: <20121025101416.v1wilj95q8wkk0os-cebfxv@webmail.spamcop.net>
Date:	Thu, 25 Oct 2012 10:14:16 -0400
From:	Pavel Roskin <proski@....org>
To:	Al Viro <viro@...iv.linux.org.uk>, linux-kernel@...r.kernel.org
Subject: Bisected regression: iterate_fd() selinux change affects flash
	plugin

Hello, Al!

I have noticed that Mozilla Firefox gets stuck for seconds or minutes  
on some sites, in particular on Facebook with Linux 3.7-rc1 and newer  
mainline kernels.  Disabling flash plugin fixes the delays.

This is a Fedora 17 system with SELinux enabled, on x86_64  
architecture, with all updates, with LXDE desktop.  It's not the  
Fedora 16 system I mentioned before, it has never had LXDE login  
problems due to replace_fd().

Bisecting lead me to the patch that introduced iterate_fd():

commit c3c073f808b22dfae15ef8412b6f7b998644139a
Author: Al Viro <viro@...iv.linux.org.uk>
Date:   Tue Aug 21 22:32:06 2012 -0400

     new helper: iterate_fd()

     iterates through the opened files in given descriptor table,
     calling a supplied function; we stop once non-zero is returned.
     Callback gets struct file *, descriptor number and const void *
     argument passed to iterator.  It is called with files->file_lock
     held, so it is not allowed to block.

     tty_io, netprio_cgroup and selinux flush_unauthorized_files()
     converted to its use.

     Signed-off-by: Al Viro <viro@...iv.linux.org.uk>

I have found that reverting the changes to security/selinux/hooks.c is  
sufficient to restore the correct behavior.

-- 
Regards,
Pavel Roskin
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