linux-kernel - Re: [PATCH v1 1/3] binder: BINDER

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Date:   Thu, 11 Mar 2021 08:33:42 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Li Li <dualli@...omium.org>
Cc:     dualli@...gle.com, tkjos@...gle.com, christian@...uner.io,
        arve@...roid.com, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, maco@...gle.com, hridya@...gle.com,
        surenb@...gle.com, joel@...lfernandes.org, kernel-team@...roid.com
Subject: Re: [PATCH v1 1/3] binder: BINDER_FREEZE ioctl

On Wed, Mar 10, 2021 at 02:52:49PM -0800, Li Li wrote:
>  	if (target_proc) {
>  		binder_inner_proc_lock(target_proc);
> +		target_proc->outstanding_txns--;
> +		WARN_ON(target_proc->outstanding_txns < 0);

WARN_* is a huge crutch, please just handle stuff like this properly and
if you really need to, warn userspace (but what can they do about it?)

You also just rebooted all systems that have panic-on-warn set, so if
this can be triggered by userspace, you caused a DoS of things :(

So please remove all of the WARN_ON() you add in this patch series to
properly handle the error conditions and deal with them correctly.

And if these were here just for debugging, hopefully the code works
properly now and you do not need debugging anymore so they can all just
be dropped.

thanks,

greg k-h