linux-kernel - Re: [PATCH v4] char: pcmcia: scr24x_cs: Fix use-after-free in scr24x

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Message-ID: <Yyg6N+yS9YyAepFk@kroah.com>
Date:   Mon, 19 Sep 2022 11:45:27 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Hyunwoo Kim <imv4bel@...il.com>
Cc:     lkundrak@...sk, linux-kernel@...r.kernel.org, arnd@...db.de,
        linux@...inikbrodowski.net
Subject: Re: [PATCH v4] char: pcmcia: scr24x_cs: Fix use-after-free in
 scr24x_fops

On Mon, Sep 19, 2022 at 02:38:01AM -0700, Hyunwoo Kim wrote:
> A race condition may occur if the user physically removes the
> pcmcia device while calling open() for this char device node.
> 
> This is a race condition between the scr24x_open() function and
> the scr24x_remove() function, which may eventually result in UAF.
> 
> So, add a mutex to the scr24x_open() and scr24x_remove() functions
> to avoid race contidion of krefs.
> 
> Signed-off-by: Hyunwoo Kim <imv4bel@...il.com>
> Reported-by: kernel test robot <lkp@...el.com>

The robot did not report this original problem :(

> ---
>  drivers/char/pcmcia/scr24x_cs.c | 73 +++++++++++++++++++++++----------
>  1 file changed, 52 insertions(+), 21 deletions(-)

You failed to put below the --- line what changed from previous versions
as the documentation asks for.

thanks,

greg k-h