linux-kernel - Re: [PATCH v2] efi: random: fix NULL-deref when refreshing seed

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Message-ID: <Y6BwVj93vv3hYoOe@hovoldconsulting.com>
Date:   Mon, 19 Dec 2022 15:08:22 +0100
From:   Johan Hovold <johan@...nel.org>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     Johan Hovold <johan+linaro@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org, Steev Klimaszewski <steev@...i.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Andrew Halaney <ahalaney@...hat.com>
Subject: Re: [PATCH v2] efi: random: fix NULL-deref when refreshing seed

On Mon, Dec 19, 2022 at 03:00:17PM +0100, Jason A. Donenfeld wrote:
> On Mon, Dec 19, 2022 at 11:12:37AM +0100, Johan Hovold wrote:
> > Do not try to refresh the RNG seed in case the firmware does not support
> > setting variables.
> > 
> > This is specifically needed to prevent a NULL-pointer dereference on the
> > Lenovo X13s with some firmware revisions, or more generally, whenever
> > the runtime services have been disabled (e.g. efi=noruntime or with
> > PREEMPT_RT).
> > 
> > Fixes: e7b813b32a42 ("efi: random: refresh non-volatile random seed when RNG is initialized")
> > Reported-by: Steev Klimaszewski <steev@...i.org>
> > Reported-by: Bjorn Andersson <andersson@...nel.org>
> > Tested-by: Andrew Halaney <ahalaney@...hat.com> # sc8280xp-lenovo-thinkpad-x13s
> > Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> > ---
> > 
> > Changes in v2
> >  - amend commit message with a comment on this being needed whenever the
> >    runtime services have been disabled
> 
> I'll queue up the one with the amended commit message.

Perfect, thanks!

Johan