netdev - Re: [PATCH] [v2] iwlwifi: pcie: fix constant-conversion warning

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Date:   Fri, 12 Nov 2021 09:17:48 +0000
From:   "Coelho, Luciano" <luciano.coelho@...el.com>
To:     "nathan@...nel.org" <nathan@...nel.org>,
        "Berg, Johannes" <johannes.berg@...el.com>,
        "arnd@...nel.org" <arnd@...nel.org>,
        "kvalo@...eaurora.org" <kvalo@...eaurora.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "ndesaulniers@...gle.com" <ndesaulniers@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>
CC:     lkp <lkp@...el.com>, "Baruch, Yaara" <yaara.baruch@...el.com>,
        "llvm@...ts.linux.dev" <llvm@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Gottlieb, Matti" <matti.gottlieb@...el.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "Grumbach, Emmanuel" <emmanuel.grumbach@...el.com>
Subject: Re: [PATCH] [v2] iwlwifi: pcie: fix constant-conversion warning

On Thu, 2021-11-11 at 08:31 +0100, Arnd Bergmann 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 extra range check makes that obvious to both readers and to the
> compiler.
> 
> Fixes: 3f7320428fa4 ("iwlwifi: pcie: simplify iwl_pci_find_dev_info()")
> Reported-by: kernel test robot <lkp@...el.com>
> Cc: Nick Desaulniers <ndesaulniers@...gle.com>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> Changes in v2:
> - replace int cast with a range check
> ---
>  drivers/net/wireless/intel/iwlwifi/pcie/drv.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/drv.c b/drivers/net/wireless/intel/iwlwifi/pcie/drv.c
> index c574f041f096..fcda7603024b 100644
> --- a/drivers/net/wireless/intel/iwlwifi/pcie/drv.c
> +++ b/drivers/net/wireless/intel/iwlwifi/pcie/drv.c
> @@ -1341,6 +1341,9 @@ iwl_pci_find_dev_info(u16 device, u16 subsystem_device,
>  {
>  	int i;
>  
> +	if (ARRAY_SIZE(iwl_dev_info_table) == 0)
> +		return NULL;
> +
>  	for (i = ARRAY_SIZE(iwl_dev_info_table) - 1; i >= 0; i--) {
>  		const struct iwl_dev_info *dev_info = &iwl_dev_info_table[i];

This looks good now.

Acked-by: Luca Coelho <luciano.coelho@...el.com>

Kalle, I'll assign it to you so you can take it to wireless-drivers
when it opens again.

Thanks!

--
Cheers,
Luca.