linux-kernel - Re: [PATCH] module: print module name on refcount error

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Message-ID: <ZKhf8bi/eBDhaihD@bombadil.infradead.org>
Date:   Fri, 7 Jul 2023 11:56:49 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Michal Hocko <mhocko@...e.com>
Cc:     Jean Delvare <jdelvare@...e.de>, linux-modules@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] module: print module name on refcount error

On Mon, Jul 03, 2023 at 03:47:22PM +0200, Michal Hocko wrote:
> On Fri 30-06-23 16:05:33, Luis Chamberlain wrote:
> [...]
> > What prevents code from racing the free with a random module_put()
> > called by some other piece of code?
> 
> Wouldn't be ref count a garbage already? How can you race when freeing
> if module_put fail?

It could yes, ie, so this risks at all being junk. So best IMHO is
to tidy up all the get / puts and add respective tests to fix all
this mess with proper messages as needed. My cursory review of the
refcnt stuf is I see some races possible.

While I'd be happy to help debugging aids, adding accesses to random
memory for a string seems more risk prone.

  Luis