Re: 4.7-rc7: use-after-free in proc_map_files_readdir

From: Dave Jones
Date: Tue Jul 19 2016 - 15:47:31 EST


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?

Will give it another run when I get home. Machine is locked up for unknown
reasons right now..

Dave