linux-kernel - Re: [PATCH 1/2] platform/x86/intel/pmc: Fix hang in pmc_core_send_ltr

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Date: Mon, 18 Dec 2023 14:30:04 +0200 (EET)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: rjingar <rajvi.jingar@...ux.intel.com>, 
    Hans de Goede <hdegoede@...hat.com>
cc: irenic.rajneesh@...il.com, david.e.box@...el.com, markgross@...nel.org, 
    platform-driver-x86@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] platform/x86/intel/pmc: Fix hang in
 pmc_core_send_ltr_ignore()

On Fri, 15 Dec 2023, rjingar wrote:

> From: Rajvi Jingar <rajvi.jingar@...ux.intel.com>
> 
> For input value 0, PMC stays unassigned which causes crash while trying
> to access PMC for register read/write. Include LTR index 0 in pmc_index
> and ltr_index calculation.
> 
> Fixes: 2bcef4529222 ("platform/x86:intel/pmc: Enable debugfs multiple PMC support")
> Signed-off-by: Rajvi Jingar <rajvi.jingar@...ux.intel.com>
> ---
>  drivers/platform/x86/intel/pmc/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/x86/intel/pmc/core.c b/drivers/platform/x86/intel/pmc/core.c
> index 983e3a8f4910..55eb6a4683fb 100644
> --- a/drivers/platform/x86/intel/pmc/core.c
> +++ b/drivers/platform/x86/intel/pmc/core.c
> @@ -474,7 +474,7 @@ int pmc_core_send_ltr_ignore(struct pmc_dev *pmcdev, u32 value)
>  	 * is based on the contiguous indexes from ltr_show output.
>  	 * pmc index and ltr index needs to be calculated from it.
>  	 */
> -	for (pmc_index = 0; pmc_index < ARRAY_SIZE(pmcdev->pmcs) && ltr_index > 0; pmc_index++) {
> +	for (pmc_index = 0; pmc_index < ARRAY_SIZE(pmcdev->pmcs) && ltr_index >= 0; pmc_index++) {
>  		pmc = pmcdev->pmcs[pmc_index];
>  
>  		if (!pmc)
> 

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

I'll have to say though I really don't like they way that function is 
playing with fire by mixing the use of signed and unsigned variables.

As is, this can only be triggered through a debugfs write and we're 
already in -rc6 so IMO next material.

-- 
 i.