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

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Date:   Mon, 19 Dec 2022 11:18:19 +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>
Subject: Re: [PATCH] efi: random: fix NULL-deref when refreshing seed

On Fri, Dec 16, 2022 at 12:39:56PM -0700, Jason A. Donenfeld wrote:
> On Fri, Dec 16, 2022 at 10:15:14AM +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.
> > 
> > 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>
> > Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> > ---
> 
> Thanks very much for this, and sorry for the breakage. I'll try to get
> this in before rc1 is cut, as I've got some other changes scheduled for
> late in the merge window to send anyway.

In case this one hasn't been picked up yet (it's not in linux-next), I
just sent a v2 with an amended commit message with an explicit mention
that as this is needed whenever the runtime services have been disabled
(e.g. with PREEMPT_RT):

	https://lore.kernel.org/lkml/20221219101237.9872-1-johan+linaro@kernel.org/

Johan