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From:   Shayne Chen <shayne.chen@mediatek.com>
To:     Felix Fietkau <nbd@nbd.name>
CC:     linux-wireless <linux-wireless@vger.kernel.org>,
        Lorenzo Bianconi <lorenzo.bianconi@redhat.com>,
        Ryder Lee <ryder.lee@mediatek.com>,
        linux-mediatek <linux-mediatek@lists.infradead.org>,
        Shayne Chen <shayne.chen@mediatek.com>,
        Bo Jiao <bo.jiao@mediatek.com>
Subject: [PATCH v2] mt76: mt7915: fix potential overflow of eeprom page index
Date:   Tue, 20 Jul 2021 10:48:32 +0800
Message-ID: <20210720024832.20265-1-shayne.chen@mediatek.com>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

If total eeprom size is divisible by per-page size, the i in for loop
will exceed max page index, which happens in our newer chipset.

Fixes: 26f18380e6ca ("mt76: mt7915: add support for flash mode")
Signed-off-by: Bo Jiao <bo.jiao@mediatek.com>
Signed-off-by: Shayne Chen <shayne.chen@mediatek.com>
Reported-by: kernel test robot <lkp@intel.com>
---
v2: fix warning reported by kernel test robot

	drivers/net/wireless/mediatek/mt76/mt7915/mcu.c:3407:22: warning: use
	of logical '&&' with constant operand [-Wconstant-logical-operand]
	if (i == total - 1 && MT7915_EEPROM_SIZE % PER_PAGE_SIZE)
			^  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
---
 drivers/net/wireless/mediatek/mt76/mt7915/mcu.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7915/mcu.c b/drivers/net/wireless/mediatek/mt76/mt7915/mcu.c
index 91efa9b..69b6796 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7915/mcu.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7915/mcu.c
@@ -3392,20 +3392,20 @@ int mt7915_mcu_set_chan_info(struct mt7915_phy *phy, int cmd)
 
 static int mt7915_mcu_set_eeprom_flash(struct mt7915_dev *dev)
 {
-#define TOTAL_PAGE_MASK		GENMASK(7, 5)
+#define MAX_PAGE_IDX_MASK	GENMASK(7, 5)
 #define PAGE_IDX_MASK		GENMASK(4, 2)
 #define PER_PAGE_SIZE		0x400
 	struct mt7915_mcu_eeprom req = { .buffer_mode = EE_MODE_BUFFER };
-	u8 total = MT7915_EEPROM_SIZE / PER_PAGE_SIZE;
+	u8 total = DIV_ROUND_UP(MT7915_EEPROM_SIZE, PER_PAGE_SIZE);
 	u8 *eep = (u8 *)dev->mt76.eeprom.data;
 	int eep_len;
 	int i;
 
-	for (i = 0; i <= total; i++, eep += eep_len) {
+	for (i = 0; i < total; i++, eep += eep_len) {
 		struct sk_buff *skb;
 		int ret;
 
-		if (i == total)
+		if (i == total - 1 && !!(MT7915_EEPROM_SIZE % PER_PAGE_SIZE))
 			eep_len = MT7915_EEPROM_SIZE % PER_PAGE_SIZE;
 		else
 			eep_len = PER_PAGE_SIZE;
@@ -3415,7 +3415,7 @@ static int mt7915_mcu_set_eeprom_flash(struct mt7915_dev *dev)
 		if (!skb)
 			return -ENOMEM;
 
-		req.format = FIELD_PREP(TOTAL_PAGE_MASK, total) |
+		req.format = FIELD_PREP(MAX_PAGE_IDX_MASK, total - 1) |
 			     FIELD_PREP(PAGE_IDX_MASK, i) | EE_FORMAT_WHOLE;
 		req.len = cpu_to_le16(eep_len);
 
-- 
2.25.1