linux-kernel - Re: [PATCH] binder: check for binder_thread allocation failure in binder

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Date:   Wed, 31 Jan 2018 11:16:51 -0800
From:   Todd Kjos <tkjos@...gle.com>
To:     Eric Biggers <ebiggers3@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        "open list:ANDROID DRIVERS" <devel@...verdev.osuosl.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs@...glegroups.com, Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH] binder: check for binder_thread allocation failure in binder_poll()

Looks good to me.

On Tue, Jan 30, 2018 at 11:11 PM, Eric Biggers <ebiggers3@...il.com> wrote:
> From: Eric Biggers <ebiggers@...gle.com>
>
> If the kzalloc() in binder_get_thread() fails, binder_poll()
> dereferences the resulting NULL pointer.
>
> Fix it by returning POLLERR if the memory allocation failed.
>
> This bug was found by syzkaller using fault injection.
>
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
> Cc: stable@...r.kernel.org
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>
> ---
>  drivers/android/binder.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index d21040c5d343f..326ca8ea9ebcf 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -4391,6 +4391,8 @@ static __poll_t binder_poll(struct file *filp,
>         bool wait_for_proc_work;
>
>         thread = binder_get_thread(proc);
> +       if (!thread)
> +               return POLLERR;
>
>         binder_inner_proc_lock(thread->proc);
>         thread->looper |= BINDER_LOOPER_STATE_POLL;
> --
> 2.16.1
>