[PATCH 4.19 128/196] net: usb: sr9700: fix uninitialized variable use in sr_mdio_read

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4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ma Ke <make24@xxxxxxxxxxx>

commit 08f3a5c38087d1569e982a121aad1e6acbf145ce upstream.

It could lead to error happen because the variable res is not updated if
the call to sr_share_read_word returns an error. In this particular case
error code was returned and res stayed uninitialized. Same issue also
applies to sr_read_reg.

This can be avoided by checking the return value of sr_share_read_word
and sr_read_reg, and propagating the error if the read operation failed.

Found by code review.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: c9b37458e956 ("USB2NET : SR9700 : One chip USB 1.1 USB2NET SR9700Device Driver Support")
Signed-off-by: Ma Ke <make24@xxxxxxxxxxx>
Reviewed-by: Shigeru Yoshida <syoshida@xxxxxxxxxx>
Reviewed-by: Hariprasad Kelam <hkelam@xxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/usb/sr9700.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/drivers/net/usb/sr9700.c
+++ b/drivers/net/usb/sr9700.c
@@ -178,6 +178,7 @@ static int sr_mdio_read(struct net_devic
 	struct usbnet *dev = netdev_priv(netdev);
 	__le16 res;
 	int rc = 0;
+	int err;
 
 	if (phy_id) {
 		netdev_dbg(netdev, "Only internal phy supported\n");
@@ -188,11 +189,17 @@ static int sr_mdio_read(struct net_devic
 	if (loc == MII_BMSR) {
 		u8 value;
 
-		sr_read_reg(dev, SR_NSR, &value);
+		err = sr_read_reg(dev, SR_NSR, &value);
+		if (err < 0)
+			return err;
+
 		if (value & NSR_LINKST)
 			rc = 1;
 	}
-	sr_share_read_word(dev, 1, loc, &res);
+	err = sr_share_read_word(dev, 1, loc, &res);
+	if (err < 0)
+		return err;
+
 	if (rc == 1)
 		res = le16_to_cpu(res) | BMSR_LSTATUS;
 	else






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