From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <jpoimboe@redhat.com>
Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28])
 (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by lists.ozlabs.org (Postfix) with ESMTPS id 3ySQx82jqWzDr5S
 for <linuxppc-dev@lists.ozlabs.org>; Fri,  3 Nov 2017 00:32:11 +1100 (AEDT)
Date: Thu, 2 Nov 2017 08:32:00 -0500
From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Miroslav Benes <mbenes@suse.cz>
Cc: jeyu@kernel.org, jikos@kernel.org, pmladek@suse.com, lpechacek@suse.cz,
 pavel@ucw.cz, live-patching@vger.kernel.org,
 linux-kernel@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>,
 Michael Ellerman <mpe@ellerman.id.au>,
 Thomas Gleixner <tglx@linutronix.de>,
 Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
 Andy Lutomirski <luto@kernel.org>, linuxppc-dev@lists.ozlabs.org,
 x86@kernel.org
Subject: Re: [PATCH v3 1/2] livepatch: send a fake signal to all blocking tasks
Message-ID: <20171102133200.abwvepjx3ytufsc4@treble>
References: <20171031114853.841-1-mbenes@suse.cz>
 <20171031114853.841-2-mbenes@suse.cz>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
In-Reply-To: <20171031114853.841-2-mbenes@suse.cz>
List-Id: Linux on PowerPC Developers Mail List <linuxppc-dev.lists.ozlabs.org>
List-Unsubscribe: <https://lists.ozlabs.org/options/linuxppc-dev>,
 <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=unsubscribe>
List-Archive: <http://lists.ozlabs.org/pipermail/linuxppc-dev/>
List-Post: <mailto:linuxppc-dev@lists.ozlabs.org>
List-Help: <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=help>
List-Subscribe: <https://lists.ozlabs.org/listinfo/linuxppc-dev>,
 <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=subscribe>

On Tue, Oct 31, 2017 at 12:48:52PM +0100, Miroslav Benes wrote:
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index bf8c8fd72589..b7c60662baf3 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -440,6 +440,7 @@ EXPORT_SYMBOL_GPL(klp_enable_patch);
>   * /sys/kernel/livepatch/<patch>
>   * /sys/kernel/livepatch/<patch>/enabled
>   * /sys/kernel/livepatch/<patch>/transition
> + * /sys/kernel/livepatch/<patch>/signal
>   * /sys/kernel/livepatch/<patch>/<object>
>   * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
>   */
> @@ -514,11 +515,37 @@ static ssize_t transition_show(struct kobject *kobj,
>  			patch == klp_transition_patch);
>  }
>  
> +static ssize_t signal_store(struct kobject *kobj, struct kobj_attribute *attr,
> +			    const char *buf, size_t count)
> +{
> +	int ret;
> +	bool val;
> +
> +	/*
> +	 * klp_mutex lock is not grabbed here intentionally. It is not really
> +	 * needed. The race window is harmless and grabbing the lock would only
> +	 * hold the action back.
> +	 */
> +	if (!klp_transition_patch)
> +		return -EINVAL;
> +
> +	ret = kstrtobool(buf, &val);
> +	if (ret)
> +		return ret;
> +
> +	if (val)
> +		klp_force_signals();
> +
> +	return count;
> +}

The function still has global functionality even though the sysfs entry
is now per-patch.  So if you do

  echo 1 > /sys/kernel/livepatch/patch1/signal

But patch2 is in transition, then it will send signals based on patch2.
Instead it should probably return an error.

There's a similar issue with force_store().

-- 
Josh