linux-kernel - [PATCH net] net: usb: lan78xx: fix use of improperly initialized dev->chipid in lan78xx

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Message-ID: <20251001131409.155650-1-viswanathiyyappan@gmail.com>
Date: Wed,  1 Oct 2025 18:44:09 +0530
From: I Viswanath <viswanathiyyappan@...il.com>
To: Thangaraj.S@...rochip.com,
	Rengarajan.S@...rochip.com,
	UNGLinuxDriver@...rochip.com,
	andrew+netdev@...n.ch,
	davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com
Cc: netdev@...r.kernel.org,
	linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	skhan@...uxfoundation.org,
	linux-kernel-mentees@...ts.linux.dev,
	david.hunter.linux@...il.com,
	I Viswanath <viswanathiyyappan@...il.com>
Subject: [PATCH net] net: usb: lan78xx: fix use of improperly initialized dev->chipid in lan78xx_reset

dev->chipid is used in lan78xx_init_mac_address before it's initialized:

lan78xx_reset() {
    lan78xx_init_mac_address()
        lan78xx_read_eeprom()
            lan78xx_read_raw_eeprom() <- dev->chipid is used here

    dev->chipid = ... <- dev->chipid is initialized correctly here
}

Reorder initialization so that dev->chipid is set before calling
lan78xx_init_mac_address().

Signed-off-by: I Viswanath <viswanathiyyappan@...il.com>
---
 
KMSAN didn't detect this issue because dev->chipid is zero
initialized from alloc_etherdev

 drivers/net/usb/lan78xx.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c
index 1ff25f57329a..f3831ecaaec1 100644
--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -3238,10 +3238,6 @@ static int lan78xx_reset(struct lan78xx_net *dev)
 		}
 	} while (buf & HW_CFG_LRST_);
 
-	ret = lan78xx_init_mac_address(dev);
-	if (ret < 0)
-		return ret;
-
 	/* save DEVID for later usage */
 	ret = lan78xx_read_reg(dev, ID_REV, &buf);
 	if (ret < 0)
@@ -3250,6 +3246,10 @@ static int lan78xx_reset(struct lan78xx_net *dev)
 	dev->chipid = (buf & ID_REV_CHIP_ID_MASK_) >> 16;
 	dev->chiprev = buf & ID_REV_CHIP_REV_MASK_;
 
+	ret = lan78xx_init_mac_address(dev);
+	if (ret < 0)
+		return ret;
+
 	/* Respond to the IN token with a NAK */
 	ret = lan78xx_read_reg(dev, USB_CFG0, &buf);
 	if (ret < 0)
-- 
2.47.3