Re: [PATCH -nect RFC v2 0/2] block: fix uaf in bd_link_disk_holder()

[Yu Kuai]

Hi, Christoph

在 2022/10/30 23:30, Christoph Hellwig 写道:
> On Fri, Oct 21, 2022 at 11:15:34AM +0800, Yu Kuai wrote:
> > Hi,
> >
> > 在 2022/10/21 0:47, Christoph Hellwig 写道:
> > > As mentioned before I don't think we should make this even more
> > > crufty in the block layer.  See the series I just sent to move it int
> > > dm.
> >
> > It seems we had some misunderstanding, the problem I tried to fix here
> > should not just related to dm, but all the caller of
> > bd_link_disk_holder().
>
> As far as I can tell the problem was just that patch 1 in my series blows
> away the bd_holder_dir pointer in part0 on del_gendisk.  Each holder
> actually holds a reference to the kobject, so the memory for it is
> still valid, it's just that the pointer got cleared.  I'll send a v2
> in a bit.

This is not the real case. In bd_link_disk_hoder(), bd_hodler_dir is
accessed first by add_symlink(), and then reference is grabed later.
The reference should be grabed before bd_holder_dir is accessed, like
what I try to do in patch 2.

Thanks,
Kuai
> .