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From: Arnd Bergmann <arnd@kernel.org>
To: Ping-Ke Shih <pkshih@realtek.com>,
	Kalle Valo <kvalo@kernel.org>,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Ching-Te Ku <ku920601@realtek.com>,
	linux-wireless@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH] rtw89: avoid stringop-overflow warning
Date: Mon,  4 Dec 2023 08:30:13 +0100
Message-Id: <20231204073020.1105416-1-arnd@kernel.org>
Precedence: bulk
MIME-Version: 1.0
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From: Arnd Bergmann <arnd@arndb.de>

After -Wstringop-overflow got enabled, the rtw89 driver produced
two odd warnings with gcc-13:

drivers/net/wireless/realtek/rtw89/coex.c: In function 'rtw89_btc_ntfy_scan_start':
drivers/net/wireless/realtek/rtw89/coex.c:5362:50: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=]
 5362 |                 wl->dbcc_info.scan_band[phy_idx] = band;
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~
In file included from drivers/net/wireless/realtek/rtw89/coex.h:8,
                 from drivers/net/wireless/realtek/rtw89/coex.c:5:
drivers/net/wireless/realtek/rtw89/core.h:1441:12: note: at offset [64, 255] into destination object 'scan_band' of size 2
 1441 |         u8 scan_band[RTW89_PHY_MAX]; /* scan band in  each phy */
      |            ^~~~~~~~~
drivers/net/wireless/realtek/rtw89/coex.c: In function 'rtw89_btc_ntfy_switch_band':
drivers/net/wireless/realtek/rtw89/coex.c:5406:50: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=]
 5406 |                 wl->dbcc_info.scan_band[phy_idx] = band;
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~
drivers/net/wireless/realtek/rtw89/core.h:1441:12: note: at offset [64, 255] into destination object 'scan_band' of size 2
 1441 |         u8 scan_band[RTW89_PHY_MAX]; /* scan band in  each phy */
      |            ^~~~~~~~~

I don't know what happened here, but adding an explicit range check
shuts up the output.

Fixes: 89741e7e42f6 ("Makefile: Enable -Wstringop-overflow globally")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/net/wireless/realtek/rtw89/coex.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/net/wireless/realtek/rtw89/coex.c b/drivers/net/wireless/realtek/rtw89/coex.c
index b842cd9a86f8..9c0db35d3e13 100644
--- a/drivers/net/wireless/realtek/rtw89/coex.c
+++ b/drivers/net/wireless/realtek/rtw89/coex.c
@@ -5352,6 +5352,10 @@ void rtw89_btc_ntfy_scan_start(struct rtw89_dev *rtwdev, u8 phy_idx, u8 band)
 	rtw89_debug(rtwdev, RTW89_DBG_BTC,
 		    "[BTC], %s(): phy_idx=%d, band=%d\n",
 		    __func__, phy_idx, band);
+
+	if (phy_idx >= RTW89_PHY_MAX)
+		return;
+
 	btc->dm.cnt_notify[BTC_NCNT_SCAN_START]++;
 	wl->status.map.scan = true;
 	wl->scan_info.band[phy_idx] = band;
@@ -5396,6 +5400,10 @@ void rtw89_btc_ntfy_switch_band(struct rtw89_dev *rtwdev, u8 phy_idx, u8 band)
 	rtw89_debug(rtwdev, RTW89_DBG_BTC,
 		    "[BTC], %s(): phy_idx=%d, band=%d\n",
 		    __func__, phy_idx, band);
+
+	if (phy_idx >= RTW89_PHY_MAX)
+		return;
+
 	btc->dm.cnt_notify[BTC_NCNT_SWITCH_BAND]++;
 
 	wl->scan_info.band[phy_idx] = band;
-- 
2.39.2