Subject: Re: [PATCH v2] memory: mtk-smi: Fix a null dereference for the ostd
To:     Yong Wu <yong.wu@mediatek.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
        Matthias Brugger <matthias.bgg@gmail.com>
Cc:     Krzysztof Kozlowski <krzk@kernel.org>,
        Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Tomasz Figa <tfiga@chromium.org>,
        linux-mediatek@lists.infradead.org, srv_heupstream@mediatek.com,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        iommu@lists.linux-foundation.org, youlin.pei@mediatek.com,
        anan.sun@mediatek.com, yi.kuo@mediatek.com,
        anthony.huang@mediatek.com, Ikjoon Jang <ikjn@chromium.org>,
        Hsin-Yi Wang <hsinyi@chromium.org>
References: <20211108082429.15080-1-yong.wu@mediatek.com>
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>
Message-ID: <1d72bac8-eb79-6f34-79ca-4c5c38d6d2bf@collabora.com>
Date:   Thu, 11 Nov 2021 14:41:37 +0100
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Il 08/11/21 09:24, Yong Wu ha scritto:
> We add the ostd setting for mt8195. It introduces a KE for the
> previous SoC which doesn't have ostd setting. This is the log:
> 
> Unable to handle kernel NULL pointer dereference at virtual address
> 0000000000000080
> ...
> pc : mtk_smi_larb_config_port_gen2_general+0x64/0x130
> lr : mtk_smi_larb_resume+0x54/0x98
> ...
> Call trace:
>   mtk_smi_larb_config_port_gen2_general+0x64/0x130
>   pm_generic_runtime_resume+0x2c/0x48
>   __genpd_runtime_resume+0x30/0xa8
>   genpd_runtime_resume+0x94/0x2c8
>   __rpm_callback+0x44/0x150
>   rpm_callback+0x6c/0x78
>   rpm_resume+0x310/0x558
>   __pm_runtime_resume+0x3c/0x88
> 
> In the code: larbostd = larb->larb_gen->ostd[larb->larbid],
> if "larb->larb_gen->ostd" is null, the "larbostd" is the offset(e.g.
> 0x80 above), it's also a valid value, then accessing "larbostd[i]" in the
> "for" loop will cause the KE above. To avoid this issue, initialize
> "larbostd" to NULL when the SoC doesn't have ostd setting.
> 
> Signed-off-by: Yong Wu <yong.wu@mediatek.com>
> ---
> change note: Reword the commit message to show why it KE. and update the
> solution via initializing "larbostd" is NULL explicitly in the non-ostd
> case.
> ---
>   drivers/memory/mtk-smi.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 

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