linux-kernel - Re: 4.7-rc7: use-after-free in proc_map_files

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Message-ID: <20160720131421.GA11083@codemonkey.org.uk>
Date:	Wed, 20 Jul 2016 09:14:21 -0400
From:	Dave Jones <davej@...emonkey.org.uk>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Alexey Dobriyan <adobriyan@...il.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: 4.7-rc7: use-after-free in proc_map_files_readdir

On Tue, Jul 19, 2016 at 08:38:57PM +0100, Al Viro wrote:
 > On Tue, Jul 19, 2016 at 02:33:27PM -0400, Dave Jones wrote:
 > >  > Could you dump the relevant part of vmlinux objdump, rather than whatever
 > >  > you've used on base.o?  Having relocations resolved makes it much easier
 > >  > to figure out...  Or just dump that vmlinux on anonftp somewhere...
 > > 
 > > http://codemonkey.org.uk/junk/vmlinux.gz
 > 
 > OK, it's actually about fetching ->f_mode in
 >                         info.mode = vma->vm_file->f_mode;
 > 
 > %r15 points contains vma->vm_file at that point, and 0x84 is the offset of
 > f_mode in struct file on your config from hell (due to spinlock_t size
 > exploding on lockdep et.al.)
 > 
 > Interesting...  Do you have a reproducer for that?

don't waste any more time on this. leaked a task struct in
a local diff to the oom-killer.

	Dave