[PATCH] [v2] 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 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 <redacted>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.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];
 

-- 
2.29.2

On Thu, 2021-11-11 at 08:31 +0100, Arnd Bergmann wrote:

This looks good now.

Acked-by: Luca Coelho <redacted>

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

Thanks!

--
Cheers,
Luca.

On Thu, Nov 11, 2021 at 8:31 AM Arnd Bergmann [off-list ref] wrote:

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 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 <redacted>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Something went wrong on my end: I thought this was a clang warning and
that I had
fixed it because it didn't come back with my v2 patch. However I now see it in
my gcc-11 test builds, so I assume this was a gcc warning all along, and that
my patch does nothing. Please disregard it if you have not already applied it.

       Arnd

Arnd Bergmann [off-list ref] wrote:

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 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 <redacted>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Luca Coelho <redacted>

Dropping v2 and taking v3 instead.

Patch set to Changes Requested.

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20211111073145.2504032-1-arnd@kernel.org/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches