linux-kernel - Re: fs: gpf in simple

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Message-ID: <20140326055350.GA21267@redhat.com>
Date:	Wed, 26 Mar 2014 01:53:50 -0400
From:	Dave Jones <davej@...hat.com>
To:	Jan Kara <jack@...e.cz>
Cc:	Sasha Levin <sasha.levin@...cle.com>,
	Al Viro <viro@...IV.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: fs: gpf in simple_setattr

On Tue, Mar 25, 2014 at 10:12:29PM +0100, Jan Kara wrote:

 > This fixes an oops triggered by trinity when it tried mounting
 > anon_inodefs which overwrote anon_inode_inode pointer while other CPU
 > has been in anon_inode_getfile() between ihold() and d_instantiate().
 > Thus effectively creating dentry pointing to an inode without holding a
 > reference to it.

<raises eyebrows>

Sasha, do you have changes to trinity's syscall/mount.c ?
It's kind of miraculous we managed to get the type arg right
there, because right now we're just passing a random address as an arg.
The only way that could work is if we randomly managed to do an allocation,
and then a seek & read from /proc/filesystems to that buffer.  If you're
lucky enough to get all those conditions right from rand() calls, you should
probably give up on kernel hacking and buy some powerball tickets.

We should add some code to make that only return strings from /proc/filesystems,
which makes me wonder if you already did that..

	Dave

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