linux-kernel - Re: [PATCH 08/21] binder: keep vma addresses type as unsigned long

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Date:   Fri, 1 Dec 2023 07:01:19 +0000
From:   Carlos Llamas <cmllamas@...gle.com>
To:     Alice Ryhl <aliceryhl@...gle.com>
Cc:     Arve Hjønnevåg <arve@...roid.com>,
        Christian Brauner <brauner@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        kernel-team@...roid.com, linux-kernel@...r.kernel.org,
        Martijn Coenen <maco@...roid.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Todd Kjos <tkjos@...roid.com>
Subject: Re: [PATCH 08/21] binder: keep vma addresses type as unsigned long

On Tue, Nov 07, 2023 at 09:08:13AM +0000, Alice Ryhl wrote:
> Carlos Llamas <cmllamas@...gle.com> writes:
> > -	seq_printf(m, " size %zd:%zd data %pK\n",
> > +	seq_printf(m, " size %zd:%zd data %lx\n",
> >  		   buffer->data_size, buffer->offsets_size,
> >  		   buffer->user_data);
> 
> This changes all of the print operations to use %lx instead of %pK,
> which means that the addresses are no longer being hidden when using
> kptr_restrict.
> 
> Since the pointers are all userspace pointers, it's not clear to me what
> the consequences of this are. However, I'd like to confirm whether this
> is an intentional change?

I confirm the change was intentional, we are giving the impression that
these are kernel pointers when they are not. However, I do think your
concern is valid. I've added a patch to v2 to deal with this.

I can tell you we are already logging the unhashed userspace addresses
in other places and we should probably fix those too.

--
Carlos Llamas