Received-SPF: pass (google.com: domain of linux-kernel+bounces-149695-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Date: Thu, 18 Apr 2024 08:12:22 +0000
In-Reply-To: <20240417191418.1341988-3-cmllamas@google.com>
Precedence: bulk
Mime-Version: 1.0
References: <20240417191418.1341988-3-cmllamas@google.com>
Message-ID: <20240418081222.3871629-1-aliceryhl@google.com>
Subject: Re: [PATCH 2/4] binder: migrate ioctl to new PF_SPAM_DETECTION
From: Alice Ryhl <aliceryhl@google.com>
To: cmllamas@google.com
Cc: aliceryhl@google.com, arve@android.com, brauner@kernel.org, 
	gregkh@linuxfoundation.org, joel@joelfernandes.org, kernel-team@android.com, 
	linux-kernel@vger.kernel.org, maco@android.com, surenb@google.com, 
	tkjos@android.com
Content-Type: text/plain; charset="utf-8"

Carlos Llamas <cmllamas@google.com> writes:
> @@ -5553,7 +5553,8 @@ static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>  			goto err;
>  		}
>  		binder_inner_proc_lock(proc);
> -		proc->oneway_spam_detection_enabled = (bool)enable;
> +		proc->flags &= ~PF_SPAM_DETECTION;
> +		proc->flags |= enable & PF_SPAM_DETECTION;

The bitwise and in `enable & PF_SPAM_DETECTION` only works because
PF_SPAM_DETECTION happens to be equal to 1. This seems pretty fragile to
me. Would you be willing to do this instead?

proc->flags &= ~PF_SPAM_DETECTION;
if (enable)
	proc->flags |= PF_SPAM_DETECTION;


Carlos Llamas <cmllamas@google.com> writes:
> -			if (proc->oneway_spam_detection_enabled &&
> -				   w->type == BINDER_WORK_TRANSACTION_ONEWAY_SPAM_SUSPECT)
> +			if (proc->flags & PF_SPAM_DETECTION &&
> +			    w->type == BINDER_WORK_TRANSACTION_ONEWAY_SPAM_SUSPECT)

Maybe I am just not sufficiently familiar with C, but I had to look up
the operator precedence rules for this one. Could we add parenthesises
around `proc->flags & PF_SPAM_DETECTION`? Or even define a macro for it?

Alice