linux-kernel - Re: [PATCH] of: fix iteration bug over CPU reg properties

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Date:	Mon, 21 Oct 2013 13:38:26 +0100
From:	Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@....com>
To:	Grant Likely <grant.likely@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Sudeep KarkadaNagesha <sudeep.karkadanagesha@....com>
Subject: Re: [PATCH] of: fix iteration bug over CPU reg properties

Hi Grant,

On 04/10/13 17:40, Grant Likely wrote:
> The size of each hwid in a cpu nodes 'reg' property is defined by the
> parents #address-cells property in the normal way. The cpu parsing code
> has a bug where it will overrun the end of the property if
> address-cells is greater than one. This commit fixes the problem by
> adjusting the array size by the number of address cells. It also makes
> sure address-cells isn't zero for that would cause an infinite loop.
> 
> Signed-off-by: Grant Likely <grant.likely@...aro.org>
> Cc: Rob Herring <rob.herring@...xeda.com>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> ---
> 
> I discovered this during code inspection. I don't think it is an actual
> bug seen in the wild, but the code does look wrong. I'd appreciate
> someone take a look and confirm that I've read the code right.
> 

Thanks for finding and fixing the bug.
I have tested this on ARM64 with 2 cell reg value using [1].

Tested-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@....com>

Regards,
Sudeep

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2013-October/206401.html

>  drivers/of/base.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index e4c9945..470b871 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -263,11 +263,11 @@ static bool __of_find_n_match_cpu_property(struct device_node *cpun,
>  	int ac, prop_len, tid;
>  	u64 hwid;
>  
> -	ac = of_n_addr_cells(cpun);
> +	ac = of_n_addr_cells(cpun) ? : OF_ROOT_NODE_ADDR_CELLS_DEFAULT;
>  	cell = of_get_property(cpun, prop_name, &prop_len);
>  	if (!cell)
>  		return false;
> -	prop_len /= sizeof(*cell);
> +	prop_len /= sizeof(*cell) * ac;
>  	for (tid = 0; tid < prop_len; tid++) {
>  		hwid = of_read_number(cell, ac);
>  		if (arch_match_cpu_phys_id(cpu, hwid)) {
> 


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