linux-kernel - Re: [PATCH] iwlwifi: pcie: fix constant-conversion warning

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Date:   Wed, 10 Nov 2021 13:38:11 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Luca Coelho <luciano.coelho@...el.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Johannes Berg <johannes.berg@...el.com>,
        Arnd Bergmann <arnd@...db.de>,
        Nathan Chancellor <nathan@...nel.org>,
        Yaara Baruch <yaara.baruch@...el.com>,
        Matti Gottlieb <matti.gottlieb@...el.com>,
        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] iwlwifi: pcie: fix constant-conversion warning

On Thu, Nov 4, 2021 at 6:37 AM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> clang points out a potential issue with integer overflow when
> the iwl_dev_info_table[] array is empty:
>
> drivers/net/wireless/intel/iwlwifi/pcie/drv.c:1344:42: error: implicit conversion from 'unsigned long' to 'int' changes value from 18446744073709551615 to -1 [-Werror,-Wconstant-conversion]
>         for (i = ARRAY_SIZE(iwl_dev_info_table) - 1; i >= 0; i--) {
>                ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
>
> This is still harmless, as the loop correctly terminates, but adding
> an (int) cast makes that clearer to the compiler.
>
> Fixes: 3f7320428fa4 ("iwlwifi: pcie: simplify iwl_pci_find_dev_info()")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/net/wireless/intel/iwlwifi/pcie/drv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/drv.c b/drivers/net/wireless/intel/iwlwifi/pcie/drv.c
> index c574f041f096..81e8f2fc4982 100644
> --- a/drivers/net/wireless/intel/iwlwifi/pcie/drv.c
> +++ b/drivers/net/wireless/intel/iwlwifi/pcie/drv.c
> @@ -1341,7 +1341,7 @@ iwl_pci_find_dev_info(u16 device, u16 subsystem_device,
>  {
>         int i;
>
> -       for (i = ARRAY_SIZE(iwl_dev_info_table) - 1; i >= 0; i--) {
> +       for (i = (int)ARRAY_SIZE(iwl_dev_info_table) - 1; i >= 0; i--) {

Perhaps `i` could be a `size_t` instead of an `int`?

size_t i = ARRAY_SIZE(iwl_dev_info_table);
while (i--) {
  ...

>                 const struct iwl_dev_info *dev_info = &iwl_dev_info_table[i];
>
>                 if (dev_info->device != (u16)IWL_CFG_ANY &&
> --
> 2.29.2
>


-- 
Thanks,
~Nick Desaulniers