Patch "wifi: rtlwifi: rtl8821ae: phy: fix an undefined bitwise shift behavior" has been added to the 5.15-stable tree

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This is a note to let you know that I've just added the patch titled

    wifi: rtlwifi: rtl8821ae: phy: fix an undefined bitwise shift behavior

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     wifi-rtlwifi-rtl8821ae-phy-fix-an-undefined-bitwise-.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 3e8cd841b34025ee4e8683fc0d707b032f39ccfc
Author: Su Hui <suhui@xxxxxxxxxxxx>
Date:   Mon Nov 27 09:35:13 2023 +0800

    wifi: rtlwifi: rtl8821ae: phy: fix an undefined bitwise shift behavior
    
    [ Upstream commit bc8263083af60e7e57c6120edbc1f75d6c909a35 ]
    
    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@xxxxxxxxxxxx>
    Acked-by: Ping-Ke Shih <pkshih@xxxxxxxxxxx>
    Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20231127013511.26694-2-suhui@xxxxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
index 5323ead30db0..fa1839d8ee55 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);*/




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