Date: Thu, 11 Jan 2018 17:37:37 +0100 (CET)
From: Jiri Kosina <jikos@kernel.org>
To: Miroslav Benes <mbenes@suse.cz>
cc: jpoimboe@redhat.com, jeyu@kernel.org, pmladek@suse.com,
        jbaron@akamai.com, live-patching@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] livepatch: add locking to force and signal
 functions
In-Reply-To: <20171221134043.32543-1-mbenes@suse.cz>
Message-ID: <nycvar.YFH.7.76.1801111737190.11852@cbobk.fhfr.pm>
References: <20171221134043.32543-1-mbenes@suse.cz>
User-Agent: Alpine 2.21 (LSU 202 2017-01-01)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org

On Thu, 21 Dec 2017, Miroslav Benes wrote:

> klp_send_signals() and klp_force_transition() do not acquire klp_mutex,
> because it seemed to be superfluous. A potential race in
> klp_send_signals() was harmless and there was nothing in
> klp_force_transition() which needed to be synchronized. That changed
> with the addition of klp_forced variable during the review process.
> 
> There is a small window now, when klp_complete_transition() does not see
> klp_forced set to true while all tasks have been already transitioned to
> the target state. module_put() is called and the module can be removed.
> 
> Acquire klp_mutex in sysfs callback to prevent it. Do the same for the
> signal sending just to be sure. There is no real downside to that.
> 
> Reported-by: Jason Baron <jbaron@akamai.com>
> Signed-off-by: Miroslav Benes <mbenes@suse.cz>

I've added two Fixes: tags and applied to for-4.16/signal-sysfs-force-v2.

Thanks,

-- 
Jiri Kosina
SUSE Labs