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

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Message-ID: <Y6Bucfoykf2lMdQQ@zx2c4.com>
Date:   Mon, 19 Dec 2022 15:00:17 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Johan Hovold <johan+linaro@...nel.org>
Cc:     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 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.

Jason