linux-kernel - Re: [PATCH] pmdomain: core: Fix error checking in genpd_dev_pm_attach_by

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Message-ID: <CAPDyKFoZiEAn8yT8a9VZqayR1=HPnMn+a51O3zUAUR3L6RXH=Q@mail.gmail.com>
Date: Thu, 8 May 2025 12:14:41 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Niklas Cassel <niklas.cassel@...aro.org>, 
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, Viresh Kumar <viresh.kumar@...aro.org>, 
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] pmdomain: core: Fix error checking in genpd_dev_pm_attach_by_id()

On Thu, 8 May 2025 at 08:29, Dan Carpenter <dan.carpenter@...aro.org> wrote:
>
> The error checking for of_count_phandle_with_args() does not handle
> negative error codes correctly.  The problem is that "index" is a u32 so
> in the condition "if (index >= num_domains)" negative error codes stored
> in "num_domains" are type promoted to very high positive values and
> "index" is always going to be valid.
>
> Test for negative error codes first and then test if "index" is valid.
>
> Fixes: 3ccf3f0cd197 ("PM / Domains: Enable genpd_dev_pm_attach_by_id|name() for single PM domain")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>

Thanks for the fix! It looks correct to me!

What puzzles me though, if this is a real problem I am sure we would
have been receiving bug reports, don't you think?

Kind regards
Uffe

> ---
>  drivers/pmdomain/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pmdomain/core.c b/drivers/pmdomain/core.c
> index cd4429653093..ff5c7f2b69ce 100644
> --- a/drivers/pmdomain/core.c
> +++ b/drivers/pmdomain/core.c
> @@ -3176,7 +3176,7 @@ struct device *genpd_dev_pm_attach_by_id(struct device *dev,
>         /* Verify that the index is within a valid range. */
>         num_domains = of_count_phandle_with_args(dev->of_node, "power-domains",
>                                                  "#power-domain-cells");
> -       if (index >= num_domains)
> +       if (num_domains < 0 || index >= num_domains)
>                 return NULL;
>
>         /* Allocate and register device on the genpd bus. */
> --
> 2.47.2
>