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

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Message-ID: <CACLa4pu4FFwKdoA8ATfmviOj0e0mAQ3U2FNEiJHCv4RfDY4ZoQ@mail.gmail.com>
Date:	Mon, 12 Nov 2012 10:20:18 -0500
From:	Eric Paris <eparis@...isplace.org>
To:	Pavel Roskin <proski@....org>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	SE-Linux <selinux@...ho.nsa.gov>
Subject: Re: Bisected regression: iterate_fd() selinux change affects flash plugin

OMG this +1 -1 stuff is nuts...

iterate_fd passes fd+1 instead of the fd for the file?  seriously?
ewwww.  I see how this patch fixes it, but still, wouldn't some magic
or negative value for no entries found be better than having to
understand the crazy logics?

/me pokes Al.

On Sun, Nov 11, 2012 at 11:50 PM, Pavel Roskin <proski@....org> wrote:
> Quoting Pavel Roskin <proski@....org>:
>
>> 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
>
>
> I've made a bugzilla entry for the bug and put a preliminary patch there.
> https://bugzilla.kernel.org/show_bug.cgi?id=50401
>
>
> --
> Regards,
> Pavel Roskin
> --
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