Messages in this thread | | | Subject | Re: [PATCH] memory: mtk-smi: Fix a null dereference for the ostd | From | Yong Wu <> | Date | Mon, 1 Nov 2021 18:40:53 +0800 |
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On Mon, 2021-11-01 at 09:45 +0100, Krzysztof Kozlowski wrote: > On 01/11/2021 07:09, Yong Wu wrote: > > On Fri, 2021-10-29 at 19:35 +0200, Krzysztof Kozlowski wrote: > > > On 28/10/2021 07:50, Yong Wu wrote: > > > > 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. > > > > > > You need to write more clearly, what you are fixing here. > > > > > > > > > > > Signed-off-by: Yong Wu <yong.wu@mediatek.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)); > > > > > > The code does not look good. You have already a dereference at > > > line > > > 244: > > > > > > const u8 *larbostd = larb->larb_gen->ostd[larb->larbid]; > > > > if larb->larb_gen->ostd is null, larbostd is the offset, e.g. 0x80 > > in > > the log above. thus, we can not use "larbostd[i]" in the "for" > > loop. > > > > sorry for the unreadable. In this case, is the change ok? > > No, it's ok, I did not check the type of ostd and it's confusing a > bit > that it is defined as a pointer to an array but you actually use it > as > array of pointers to 32-elemenet arrays... Anyway I was mistaken and > there will be indeed no dereference at the assignment, but for code > clarity I would still prefer to do the check earlier, so: > > > > > or like this: > > > > -const u8 *larbostd = larb->larb_gen->ostd[larb->larbid]; > > +const u8 *larbostd = larb->larb_gen->ostd ? larb->larb_gen- > > ostd[larb- > > > larbid] : NULL; > > Although I think now the proper type should be explicit. > mtk_smi_larb_mt8195_ostd is an 28-element array of > SMI_LARB_PORT_NR_MAX-element u8 arrays, therefore struct > mtk_smi_larb_gen should be: > const u8 (*ostd)[][SMI_LARB_PORT_NR_MAX];
mt8195_ostd only is a 2 dimensional array, static const u8 mtk_smi_larb_mt8195_ostd[][SMI_LARB_PORT_NR_MAX];
If using this, it will cause build fail:
.../drivers/memory/mtk-smi.c:359:23: error: initialization from incompatible pointer type [-Werror=incompatible-pointer-types] .ostd = mtk_smi_larb_mt8195_ostd, ^~~~~~~~~~~~~~~~~~~~~~~~
More background about this 2 dimensional array: The platform have many larbs(up to MTK_LARB_NR_MAX), each a larb have many ports(up to SMI_LARB_PORT_NR_MAX). In the function(*_config_port_gen2_general), we will update the value for each a port inside a larb, thus we need a pointer point to the line of that larb.
If I miss something, please tell me. or how to manage this will be better.
Thanks.
> > Right? > > > Best regards, > Krzysztof
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