From bc8263083af60e7e57c6120edbc1f75d6c909a35 Mon Sep 17 00:00:00 2001
From: Su Hui <suhui@nfschina.com>
Date: Mon, 27 Nov 2023 09:35:13 +0800
Subject: [PATCH] wifi: rtlwifi: rtl8821ae: phy: fix an undefined bitwise shift behavior
Git-commit: bc8263083af60e7e57c6120edbc1f75d6c909a35
Patch-mainline: v6.8-rc1
References: git-fixes
Clang static checker warns:
drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c:184:49:
The result of the left shift is undefined due to shifting by '32',
which is greater or equal to the width of type 'u32'.
[core.UndefinedBinaryOperatorResult]
If the value of the right operand is negative or is greater than or
equal to the width of the promoted left operand, the behavior is
undefined.[1][2]
For example, when using different gcc's compilation optimization options
(-O0 or -O2), the result of '(u32)data << 32' is different. One is 0, the
other is old value of data. Let _rtl8821ae_phy_calculate_bit_shift()'s
return value less than 32 to fix this problem. Warn if bitmask is zero.
[1] https://stackoverflow.com/questions/11270492/what-does-the-c-standard-say-about-bitshifting-more-bits-than-the-width-of-type
[2] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf
Fixes: 21e4b0726dc6 ("rtlwifi: rtl8821ae: Move driver from staging to regular tree")
Signed-off-by: Su Hui <suhui@nfschina.com>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20231127013511.26694-2-suhui@nfschina.com
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
index 6df270e29e66..68c3fb0395ce 100644
--- a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
+++ b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
@@ -29,9 +29,10 @@ static void _rtl8821ae_phy_rf_serial_write(struct ieee80211_hw *hw,
u32 data);
static u32 _rtl8821ae_phy_calculate_bit_shift(u32 bitmask)
{
- u32 i = ffs(bitmask);
+ if (WARN_ON_ONCE(!bitmask))
+ return 0;
- return i ? i - 1 : 32;
+ return __ffs(bitmask);
}
static bool _rtl8821ae_phy_bb8821a_config_parafile(struct ieee80211_hw *hw);
/*static bool _rtl8812ae_phy_config_mac_with_headerfile(struct ieee80211_hw *hw);*/
--
2.35.3