[PATCH] iwlwifi: pcie: fix constant-conversion warning

From: Arnd Bergmann <arnd@arndb.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@arndb.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--) {
 		const struct iwl_dev_info *dev_info = &iwl_dev_info_table[i];
 
 		if (dev_info->device != (u16)IWL_CFG_ANY &&

-- 
2.29.2

On Thu, Nov 4, 2021 at 6:37 AM Arnd Bergmann [off-list ref] wrote:

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

On Wed, Nov 10, 2021 at 1:38 PM Nick Desaulniers
[off-list ref] wrote:

On Thu, Nov 4, 2021 at 6:37 AM Arnd Bergmann [off-list ref] wrote:

quoted

From: Arnd Bergmann <arnd@arndb.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@arndb.de>

Also, looks like 0day bot reported as well:
https://lore.kernel.org/lkml/202111070825.gigxmmDq-lkp@intel.com/

Reported-by: kernel test robot <redacted>


-- 
Thanks,
~Nick Desaulniers

On Wed, Nov 10, 2021 at 10:38 PM Nick Desaulniers
[off-list ref] wrote:

On Thu, Nov 4, 2021 at 6:37 AM Arnd Bergmann [off-list ref] wrote:

quoted

From: Arnd Bergmann <arnd@arndb.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@arndb.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--) {
  ...

I imagine 'i' is idiomatically 'int' in inner iterations.

I've sent a different fix now.

        Arnd