linux-kernel - Re: [PATCH v2 2/4] firmware: qcom: uefisecapp: add support for R/O UEFI vars

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Message-ID: <aFlqGMWwx8ID_SaN@hovoldconsulting.com>
Date: Mon, 23 Jun 2025 16:52:08 +0200
From: Johan Hovold <johan@...nel.org>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
	Bjorn Andersson <andersson@...nel.org>,
	Maximilian Luz <luzmaximilian@...il.com>,
	Konrad Dybcio <konradybcio@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 2/4] firmware: qcom: uefisecapp: add support for R/O
 UEFI vars

On Mon, Jun 23, 2025 at 04:49:22PM +0200, Konrad Dybcio wrote:
> On 6/23/25 4:45 PM, Johan Hovold wrote:

> > It looks like the efivars implementation does not support read-only
> > efivars and this will lead to NULL pointer dereferences whenever you try
> > to write a variable.
> 
> There's efivar_supports_writes() that is used to set the EFIVAR_OPS_RDONLY
> flag which then sets SB_RDONLY on all efivarfs superblocks

Yep, but it doesn't help when attempting to store the RTC offset from
the kernel (since that does not use efivarfs).

Johan