linux-kernel - Re: [PATCH v1] drivers:base:Fix unsigned compared with less than zero

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Message-ID: <20230614-passcode-stimulate-70eecb6d81d2@spud>
Date:   Wed, 14 Jun 2023 15:33:33 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Wang Ming <machel@...o.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, opensource.kernel@...o.com
Subject: Re: [PATCH v1] drivers:base:Fix unsigned compared with less than zero

Hey,

On Wed, Jun 14, 2023 at 09:35:36PM +0800, Wang Ming wrote:
> The return value of the of_count_cache_leaves() is long.
> However, the return value is being assigned to an unsigned
> long variable 'leaves',so making 'leaves' to long.

But you actually made it an int?

> silence the warning:
> ./drivers/base/cacheinfo.c:300:5-11: WARNING: Unsigned expression
> compared with zero: leaves > 0

I'm dumb, why is comparing an unsigned value with zero a problem in and
of itself? Zero is a valid value for an unsigned type, no?

If you actually look at the function, it only returns positive, non-zero
values anyway, so returning an int is a bit pointless, as are the
checks, no?

> 
> Signed-off-by: Wang Ming <machel@...o.com>
> ---
>  drivers/base/cacheinfo.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
> index cbae8be1f..7280d5cb3 100644
> --- a/drivers/base/cacheinfo.c
> +++ b/drivers/base/cacheinfo.c
> @@ -289,7 +289,8 @@ int init_of_cache_level(unsigned int cpu)
>         struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
>         struct device_node *np = of_cpu_device_node_get(cpu);
>         struct device_node *prev = NULL;
> -       unsigned int levels = 0, leaves, level;
> +       unsigned int levels = 0, level;
> +       int leaves;
> 
>         if (!of_check_cache_nodes(np)) {
>                 of_node_put(np);
> --
> 2.25.1
> 
> 
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^^^
Gotta sort this out chief, I should probably be deleting this, not
replying to it...

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