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From:   Ping-Ke Shih <pkshih@realtek.com>
To:     <kvalo@kernel.org>
CC:     <linux-wireless@vger.kernel.org>
Subject: [PATCH] wifi: rtw89: use FIELD_PREP to fill MAC quota value
Date:   Thu, 3 Nov 2022 15:24:20 +0800
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Coverity reported shift 16 bits could cause sign extension and might get
an unexpected value. Since the input values are predefined and no this
kind of case, original code is safe so far. But, still changing them to
use FIELD_PREP() will be more clear and prevent mistakes in the future.

The original message of Coverity is:
  Suspicious implicit sign extension: "max_cfg->cma0_dma" with type "u16"
  (16 bits, unsigned) is promoted in "max_cfg->cma0_dma << 16" to type
  "int" (32 bits, signed), then sign-extended to type "unsigned long"
  (64 bits, unsigned).  If "max_cfg->cma0_dma << 16" is greater than
  0x7FFFFFFF, the upper bits of the result will all be 1."

Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
Addresses-Coverity-ID: 1527095 ("Integer handling issues")
Fixes: e3ec7017f6a2 ("rtw89: add Realtek 802.11ax driver")
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
---
 drivers/net/wireless/realtek/rtw89/mac.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtw89/mac.c b/drivers/net/wireless/realtek/rtw89/mac.c
index bb49033b587d2..11081dfdfb172 100644
--- a/drivers/net/wireless/realtek/rtw89/mac.c
+++ b/drivers/net/wireless/realtek/rtw89/mac.c
@@ -1487,10 +1487,8 @@ static int dle_mix_cfg(struct rtw89_dev *rtwdev, const struct rtw89_dle_mem *cfg
 #define INVALID_QT_WCPU U16_MAX
 #define SET_QUOTA_VAL(_min_x, _max_x, _module, _idx)			\
 	do {								\
-		val = ((_min_x) &					\
-		       B_AX_ ## _module ## _MIN_SIZE_MASK) |		\
-		      (((_max_x) << 16) &				\
-		       B_AX_ ## _module ## _MAX_SIZE_MASK);		\
+		val = FIELD_PREP(B_AX_ ## _module ## _MIN_SIZE_MASK, _min_x) | \
+		      FIELD_PREP(B_AX_ ## _module ## _MAX_SIZE_MASK, _max_x);  \
 		rtw89_write32(rtwdev,					\
 			      R_AX_ ## _module ## _QTA ## _idx ## _CFG,	\
 			      val);					\
-- 
2.25.1