linux-kernel - Re: kernel BUG at drivers/android/binder

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Message-ID: <CAHRSSEzAv_jVBsP9U6Nb3uDnXEwH1Q6ef0fTrxLNTjAV0HeHng@mail.gmail.com>
Date:   Fri, 28 Jun 2019 09:55:42 -0700
From:   Todd Kjos <tkjos@...gle.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     syzbot <syzbot+3ae18325f96190606754@...kaller.appspotmail.com>,
        Arve Hjønnevåg <arve@...roid.com>,
        Christian Brauner <christian@...uner.io>,
        "open list:ANDROID DRIVERS" <devel@...verdev.osuosl.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Martijn Coenen <maco@...roid.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Todd Kjos <tkjos@...roid.com>
Subject: Re: kernel BUG at drivers/android/binder_alloc.c:LINE! (4)

On Tue, Jun 18, 2019 at 10:37 AM Todd Kjos <tkjos@...gle.com> wrote:
>
> On Tue, Jun 18, 2019 at 5:18 AM Dan Carpenter <dan.carpenter@...cle.com> wrote:
> >
> > It's weird that that binder_alloc_copy_from_buffer() is a void function.
> > It would be easier to do the error handling at that point, instead of in
> > the callers.  It feels like we keep hitting similar bugs to this.

I took your advice. Fix posted: https://lkml.org/lkml/2019/6/28/857

-Todd

>
> The idea is that if it is an error that the user can cause, it is
> checked by the caller of binder_alloc_copy_from_buffer(). Most uses
> are kernel cases where the expected alignments should be fine and it's
> a BUG if they are not.
>
> Admittedly, a few cases (like this one) have slipped through since
> they cannot happen in Android (syzkaller has been very useful to find
> our bad assumptions).
>
> -Todd
>
> >
> > regards,
> > dan carpenter
> >