Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Wed, 7 Apr 2021 18:48:03 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Josh Poimboeuf <jpoimboe@redhat.com>
Cc:     Miroslav Benes <mbenes@suse.cz>,
        Greg KH <gregkh@linuxfoundation.org>,
        Luis Chamberlain <mcgrof@kernel.org>, mbenes@suse.com,
        Minchan Kim <minchan@kernel.org>, keescook@chromium.org,
        dhowells@redhat.com, hch@infradead.org, ngupta@vflare.org,
        sergey.senozhatsky.work@gmail.com, axboe@kernel.dk,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        live-patching@vger.kernel.org, Jessica Yu <jeyu@kernel.org>
Subject: Re: [PATCH 1/2] zram: fix crashes due to use of cpu hotplug
 multistate
Message-ID: <YG3iQ82gYkcp4G5Q@hirez.programming.kicks-ass.net>
References: <YFkWMZ0m9nKCT69T@google.com>
 <20210401235925.GR4332@42.do-not-panic.com>
 <YGbNpLKXfWpy0ZZa@kroah.com>
 <20210402183016.GU4332@42.do-not-panic.com>
 <YGgHg7XCHD3rATIK@kroah.com>
 <20210406003152.GZ4332@42.do-not-panic.com>
 <alpine.LSU.2.21.2104061354110.10372@pobox.suse.cz>
 <20210406155423.t7dagp24bupudv3p@treble>
 <YG29KAuOHbJd3Bll@hirez.programming.kicks-ass.net>
 <20210407153031.m4gg3rsgwlr432ba@treble>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20210407153031.m4gg3rsgwlr432ba@treble>
Precedence: bulk

On Wed, Apr 07, 2021 at 10:30:31AM -0500, Josh Poimboeuf wrote:
> On Wed, Apr 07, 2021 at 04:09:44PM +0200, Peter Zijlstra wrote:
> > On Tue, Apr 06, 2021 at 10:54:23AM -0500, Josh Poimboeuf wrote:
> > 
> > > Same for Red Hat.  Unloading livepatch modules seems to work fine, but
> > > isn't officially supported.
> > > 
> > > That said, if rmmod is just considered a development aid, and we're
> > > going to be ignoring bugs, we should make it official with a new
> > > TAINT_RMMOD.
> > 
> > Another option would be to have live-patch modules leak a module
> > reference by default, except when some debug sysctl is set or something.
> > Then only those LP modules loaded while the sysctl is set to 'YOLO' can
> > be unloaded.
> 
> The issue is broader than just live patching.
> 
> My suggestion was that if we aren't going to fix bugs in kernel module
> unloading, then unloading modules shouldn't be supported, and should
> taint the kernel.

Hold up, what? However much I dislike modules (and that is lots), if you
don't want to support rmmod, you have to leak a reference to self in
init. Barring that you get to fix any and all unload bugs.