Re: [PATCH] [v3] iwlwifi: pcie: fix constant-conversion warning
From: Nathan Chancellor <nathan@kernel.org>
Date: 2021-11-18 16:04:08
Also in:
lkml, llvm, netdev
On Thu, Nov 18, 2021 at 03:21:02PM +0100, Arnd Bergmann wrote:
From: Arnd Bergmann <arnd@arndb.de>
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 <redacted>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>Regardless of above, this resolves the warning for clang. Reviewed-by: Nathan Chancellor <nathan@kernel.org>
quoted hunk ↗ jump to hunk
--- 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