netdev - Re: [PATCH v5 10/27] cxl: harden resource_contains checks to handle zero size resources

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Message-ID: <20241121091347.0000233c.zhiwang@kernel.org>
Date: Thu, 21 Nov 2024 09:13:47 +0200
From: Zhi Wang <zhiwang@...nel.org>
To: Alejandro Lucero Palau <alucerop@....com>
Cc: Zhi Wang <zhiw@...dia.com>, alejandro.lucero-palau@....com,
 linux-cxl@...r.kernel.org, netdev@...r.kernel.org,
 dan.j.williams@...el.com, martin.habets@...inx.com, edward.cree@....com,
 davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
 edumazet@...gle.com
Subject: Re: [PATCH v5 10/27] cxl: harden resource_contains checks to handle
 zero size resources

On Wed, 20 Nov 2024 13:45:54 +0000
Alejandro Lucero Palau <alucerop@....com> wrote:

> 
> On 11/19/24 19:50, Zhi Wang wrote:
> > On Mon, 18 Nov 2024 16:44:17 +0000
> > <alejandro.lucero-palau@....com> wrote:
> >
> >> From: Alejandro Lucero <alucerop@....com>
> >>
> >> For a resource defined with size zero, resource_contains returns
> >> always true.
> >>
> >> Add resource size check before using it.
> >>
> > Does this trigger a bug? Looks like this should be with a Fixes:
> > tag?
> 
> 
> It seems it does not until the new code for type2 support.
> 

I see. Then it is not necessary for a Fixes: tag.

> 
> > Z.
> >
> >> Signed-off-by: Alejandro Lucero <alucerop@....com>
> >> ---
> >>   drivers/cxl/core/hdm.c | 7 +++++--
> >>   1 file changed, 5 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> >> index 223c273c0cd1..c58d6b8f9b58 100644
> >> --- a/drivers/cxl/core/hdm.c
> >> +++ b/drivers/cxl/core/hdm.c
> >> @@ -327,10 +327,13 @@ static int __cxl_dpa_reserve(struct
> >> cxl_endpoint_decoder *cxled, cxled->dpa_res = res;
> >>   	cxled->skip = skipped;
> >>   
> >> -	if (resource_contains(&cxlds->pmem_res, res))
> >> +	if (resource_size(&cxlds->pmem_res) &&
> >> +	    resource_contains(&cxlds->pmem_res, res)) {
> >>   		cxled->mode = CXL_DECODER_PMEM;
> >> -	else if (resource_contains(&cxlds->ram_res, res))
> >> +	} else if (resource_size(&cxlds->ram_res) &&
> >> +		   resource_contains(&cxlds->ram_res, res)) {
> >>   		cxled->mode = CXL_DECODER_RAM;
> >> +	}
> >>   	else {
> >>   		dev_warn(dev, "decoder%d.%d: %pr mixed mode not
> >> supported\n", port->id, cxled->cxld.id, cxled->dpa_res);
>