linux-kernel - [PATCH] memory: mtk-smi: Fix a null dereference for the ostd

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Date:   Thu, 28 Oct 2021 13:50:56 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Matthias Brugger <matthias.bgg@...il.com>
CC:     Krzysztof Kozlowski <krzk@...nel.org>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        "Tomasz Figa" <tfiga@...omium.org>,
        <linux-mediatek@...ts.infradead.org>,
        <srv_heupstream@...iatek.com>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <iommu@...ts.linux-foundation.org>, <yong.wu@...iatek.com>,
        <youlin.pei@...iatek.com>, <anan.sun@...iatek.com>,
        <yi.kuo@...iatek.com>, <anthony.huang@...iatek.com>,
        Ikjoon Jang <ikjn@...omium.org>
Subject: [PATCH] memory: mtk-smi: Fix a null dereference for the ostd

We add the ostd setting for mt8195. It introduces a abort 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, it is
also a valid value, thus, use the larb->larb_gen->ostd as the condition
inside the "for" loop.

Signed-off-by: Yong Wu <yong.wu@...iatek.com>
---
Hi Krzysztof,
Could you help review and conside this as a fix for the mt8195 patchset?
The mt8195 patchset are not in mainline, thus, I don't know its sha-id,
and don't add Fixes tag.
Thanks
---
 drivers/memory/mtk-smi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/memory/mtk-smi.c b/drivers/memory/mtk-smi.c
index b883dcc0bbfa..0262a59a2d6e 100644
--- a/drivers/memory/mtk-smi.c
+++ b/drivers/memory/mtk-smi.c
@@ -257,7 +257,7 @@ static void mtk_smi_larb_config_port_gen2_general(struct device *dev)
 	if (MTK_SMI_CAPS(flags_general, MTK_SMI_FLAG_SW_FLAG))
 		writel_relaxed(SMI_LARB_SW_FLAG_1, larb->base + SMI_LARB_SW_FLAG);
 
-	for (i = 0; i < SMI_LARB_PORT_NR_MAX && larbostd && !!larbostd[i]; i++)
+	for (i = 0; i < SMI_LARB_PORT_NR_MAX && larb->larb_gen->ostd && !!larbostd[i]; i++)
 		writel_relaxed(larbostd[i], larb->base + SMI_LARB_OSTDL_PORTx(i));
 
 	for_each_set_bit(i, (unsigned long *)larb->mmu, 32) {
-- 
2.18.0