On Thu, Nov 18, 2021 at 03:21:02PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> gcc-11 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--) {
> ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
For what it's worth, I do see this warning with Clang when both
CONFIG_IWLDVM and CONFIG_IWLMVM are disabled and looking through the GCC
warning docs [1], I do not see a -Wconstant-conversion option? Maybe
there is another warning that is similar but that warning right there
appears to have come from clang, as it matches mine exactly.
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--) {
~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
1 error generated.
[1]: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
> 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@xxxxxxxxx>
> Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Regardless of above, this resolves the warning for clang.
Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> ---
> Changes in v3:
> - make it actually work with gcc-11
> - fix commit message s/clang/gcc-11/
>
> Changes in v2:
> - replace int cast with a range check
> ---
> drivers/net/wireless/intel/iwlwifi/pcie/drv.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/drv.c b/drivers/net/wireless/intel/iwlwifi/pcie/drv.c
> index c574f041f096..395e328c6a07 100644
> --- a/drivers/net/wireless/intel/iwlwifi/pcie/drv.c
> +++ b/drivers/net/wireless/intel/iwlwifi/pcie/drv.c
> @@ -1339,9 +1339,13 @@ iwl_pci_find_dev_info(u16 device, u16 subsystem_device,
> u16 mac_type, u8 mac_step,
> u16 rf_type, u8 cdb, u8 rf_id, u8 no_160, u8 cores)
> {
> + int num_devices = ARRAY_SIZE(iwl_dev_info_table);
> int i;
>
> - for (i = ARRAY_SIZE(iwl_dev_info_table) - 1; i >= 0; i--) {
> + if (!num_devices)
> + return NULL;
> +
> + for (i = num_devices - 1; i >= 0; i--) {
> const struct iwl_dev_info *dev_info = &iwl_dev_info_table[i];
>
> if (dev_info->device != (u16)IWL_CFG_ANY &&
> --
> 2.29.2
>
