linux-kernel - Re: [RFC PATCH 2/3] Revert "android: binder: stop saving a pointer to the VMA"

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Date:   Thu, 18 May 2023 17:03:36 +0000
From:   Carlos Llamas <cmllamas@...gle.com>
To:     "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Christian Brauner <brauner@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        linux-mm@...ck.org
Subject: Re: [RFC PATCH 2/3] Revert "android: binder: stop saving a pointer
 to the VMA"

On Thu, May 18, 2023 at 10:40:52AM -0400, Liam R. Howlett wrote:
> 
> I came across this [1] when I was looking into something else and
> thought I'd double back and make sure your fix for this UAF is also
> included, since your revert will restore this bug.
> 
> I do still see the mmap_read_lock() in binder_update_page_range() vs the
> required mmap_write_lock(), at least in my branch.
> 
> [1] https://lore.kernel.org/all/20221104175450.306810-1-cmllamas@google.com/
> 

Thanks Liam, I believe you are correct. The UAF should trigger on newer
releases after the revert of your patch. I'll try to reproduce the issue
to confirm and will send the fix afterwards. This was a nice find!

Thanks,
--
Carlos Llamas