linux-hardening - Re: [PATCH v4 06/11] firmware: qcom: scm: remove unused arguments to the shm

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Message-ID: <246da659-2add-4ccf-b914-f737fb93f3f2@quicinc.com>
Date: Mon, 5 May 2025 16:28:51 +0530
From: Kuldeep Singh <quic_kuldsing@...cinc.com>
To: Amirreza Zarrabi <amirreza.zarrabi@....qualcomm.com>,
        Jens Wiklander
	<jens.wiklander@...aro.org>,
        Sumit Garg <sumit.garg@...nel.org>,
        "Bjorn
 Andersson" <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        Apurupa Pattapu
	<quic_apurupa@...cinc.com>,
        Kees Cook <kees@...nel.org>,
        "Gustavo A. R.
 Silva" <gustavoars@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>
CC: <linux-arm-msm@...r.kernel.org>, <op-tee@...ts.trustedfirmware.org>,
        <linux-kernel@...r.kernel.org>, <linux-hardening@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>, <linaro-mm-sig@...ts.linaro.org>,
        <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v4 06/11] firmware: qcom: scm: remove unused arguments to
 the shm_brige

On 4/29/2025 11:36 AM, Amirreza Zarrabi wrote:
> shm_bridge create/delete functions always use the scm device.
> There is no need to pass it as an argument.
> 
> Signed-off-by: Amirreza Zarrabi <amirreza.zarrabi@....qualcomm.com>

There are 2 type of APIs exposed by tzmem driver for pool creation.
devm_qcom_tzmem_pool_new and qcom_tzmem_pool_new.

Device managed pool is created with devm_qcom_tzmem_pool_new but
currently qcom_scm is using it's own dev to create/delete bridge which
is problamatic here.

https://elixir.bootlin.com/linux/v6.14.5/source/drivers/firmware/qcom/qcom_scm.c#L1653

If pool is device managed, same dev should be used in qcom_scm to
create/delete bridge rather than using qcom_scm dev.
The dev passed as an argument to function should be used instead of
__scm->dev.
https://elixir.bootlin.com/linux/v6.14.5/source/drivers/firmware/qcom/qcom_scm.c#L1634

To summarize, I believe correct solution should be to pass corresponding
dev to bridge create/delete APIs instead of always assuming to be
qcom_scm dev for devm_qcom_tzmem_pool_new scenarios.
For qcom_tzmem_pool_new, qcom_scm/qcom_tzmem_dev can be used.

Bartosz/Amirreza, please share your thoughts as well.

-- 
Regards
Kuldeep