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From:   Todd Kjos <tkjos@google.com>
Date:   Mon, 15 Jul 2019 13:36:22 -0700
Message-ID: <CAHRSSEwUJvO-iG6D-w8RUCi9S+iBRrX9pN3oJ=SbcHLHd0b74A@mail.gmail.com>
Subject: Re: [PATCH] binder: prevent transactions to context manager from its
 own process.
To:     Hridya Valsaraju <hridya@google.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        =?UTF-8?B?QXJ2ZSBIasO4bm5ldsOlZw==?= <arve@android.com>,
        Todd Kjos <tkjos@android.com>,
        Martijn Coenen <maco@android.com>,
        Joel Fernandes <joel@joelfernandes.org>,
        Christian Brauner <christian@brauner.io>,
        "open list:ANDROID DRIVERS" <devel@driverdev.osuosl.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Android Kernel Team <kernel-team@android.com>,
        syzbot <syzbot+8b3c354d33c4ac78bfad@syzkaller.appspotmail.com>
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On Mon, Jul 15, 2019 at 12:18 PM Hridya Valsaraju <hridya@google.com> wrote:
>
> Currently, a transaction to context manager from its own process
> is prevented by checking if its binder_proc struct is the same as
> that of the sender. However, this would not catch cases where the
> process opens the binder device again and uses the new fd to send
> a transaction to the context manager.
>
> Reported-by: syzbot+8b3c354d33c4ac78bfad@syzkaller.appspotmail.com
> Signed-off-by: Hridya Valsaraju <hridya@google.com>

Acked-by: Todd Kjos <tkjos@google.com>

> ---
>  drivers/android/binder.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index e4d25ebec5be..89b9cedae088 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -3138,7 +3138,7 @@ static void binder_transaction(struct binder_proc *proc,
>                         else
>                                 return_error = BR_DEAD_REPLY;
>                         mutex_unlock(&context->context_mgr_node_lock);
> -                       if (target_node && target_proc == proc) {
> +                       if (target_node && target_proc->pid == proc->pid) {
>                                 binder_user_error("%d:%d got transaction to context manager from process owning it\n",
>                                                   proc->pid, thread->pid);
>                                 return_error = BR_FAILED_REPLY;
> --
> 2.22.0.510.g264f2c817a-goog
>