[PATCH net-next] net: asix: add proper error handling of usb read errors

[Pavel Skripkin <paskripkin@gmail.com>]

Syzbot once again hit uninit value in asix driver. The problem still the
same -- asix_read_cmd() reads less bytes, than was requested by caller.

Since all read requests are performed via asix_read_cmd() let's catch
usb related error there and add __must_check notation to be sure all
callers actually check return value.

So, this patch adds sanity check inside asix_read_cmd(), that simply
checks if bytes read are not less, than was requested and adds missing
error handling of asix_read_cmd() all across the driver code.

Fixes: d9fe64e51114 ("net: asix: Add in_pm parameter")
Reported-and-tested-by: syzbot+6ca9f7867b77c2d316ac@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Tested-by: Oleksij Rempel <o.rempel@pengutronix.de>
---

Changes since RFT:
	- Added Tested-by: tag

---
 drivers/net/usb/asix.h         |  4 ++--
 drivers/net/usb/asix_common.c  | 19 +++++++++++++------
 drivers/net/usb/asix_devices.c | 21 ++++++++++++++++++---
 3 files changed, 33 insertions(+), 11 deletions(-)

diff --git a/drivers/net/usb/asix.h b/drivers/net/usb/asix.h
index 2a1e31def..4334aafab 100644
--- a/drivers/net/usb/asix.h
+++ b/drivers/net/usb/asix.h
@@ -192,8 +192,8 @@ extern const struct driver_info ax88172a_info;
 /* ASIX specific flags */
 #define FLAG_EEPROM_MAC		(1UL << 0)  /* init device MAC from eeprom */
 
-int asix_read_cmd(struct usbnet *dev, u8 cmd, u16 value, u16 index,
-		  u16 size, void *data, int in_pm);
+int __must_check asix_read_cmd(struct usbnet *dev, u8 cmd, u16 value, u16 index,
+			       u16 size, void *data, int in_pm);
 
 int asix_write_cmd(struct usbnet *dev, u8 cmd, u16 value, u16 index,
 		   u16 size, void *data, int in_pm);
diff --git a/drivers/net/usb/asix_common.c b/drivers/net/usb/asix_common.c
index 71682970b..524805285 100644
--- a/drivers/net/usb/asix_common.c
+++ b/drivers/net/usb/asix_common.c
@@ -11,8 +11,8 @@
 
 #define AX_HOST_EN_RETRIES	30
 
-int asix_read_cmd(struct usbnet *dev, u8 cmd, u16 value, u16 index,
-		  u16 size, void *data, int in_pm)
+int __must_check asix_read_cmd(struct usbnet *dev, u8 cmd, u16 value, u16 index,
+			       u16 size, void *data, int in_pm)
 {
 	int ret;
 	int (*fn)(struct usbnet *, u8, u8, u16, u16, void *, u16);
@@ -27,9 +27,12 @@ int asix_read_cmd(struct usbnet *dev, u8 cmd, u16 value, u16 index,
 	ret = fn(dev, cmd, USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
 		 value, index, data, size);
 
-	if (unlikely(ret < 0))
+	if (unlikely(ret < size)) {
+		ret = ret < 0 ? ret : -ENODATA;
+
 		netdev_warn(dev->net, "Failed to read reg index 0x%04x: %d\n",
 			    index, ret);
+	}
 
 	return ret;
 }
@@ -79,7 +82,7 @@ static int asix_check_host_enable(struct usbnet *dev, int in_pm)
 				    0, 0, 1, &smsr, in_pm);
 		if (ret == -ENODEV)
 			break;
-		else if (ret < sizeof(smsr))
+		else if (ret < 0)
 			continue;
 		else if (smsr & AX_HOST_EN)
 			break;
@@ -579,8 +582,12 @@ int asix_mdio_read_nopm(struct net_device *netdev, int phy_id, int loc)
 		return ret;
 	}
 
-	asix_read_cmd(dev, AX_CMD_READ_MII_REG, phy_id,
-		      (__u16)loc, 2, &res, 1);
+	ret = asix_read_cmd(dev, AX_CMD_READ_MII_REG, phy_id,
+			    (__u16)loc, 2, &res, 1);
+	if (ret < 0) {
+		mutex_unlock(&dev->phy_mutex);
+		return ret;
+	}
 	asix_set_hw_mii(dev, 1);
 	mutex_unlock(&dev->phy_mutex);
 
diff --git a/drivers/net/usb/asix_devices.c b/drivers/net/usb/asix_devices.c
index 9b72334aa..6ea44e537 100644
--- a/drivers/net/usb/asix_devices.c
+++ b/drivers/net/usb/asix_devices.c
@@ -755,7 +755,12 @@ static int ax88772_bind(struct usbnet *dev, struct usb_interface *intf)
 	priv->phy_addr = ret;
 	priv->embd_phy = ((priv->phy_addr & 0x1f) == 0x10);
 
-	asix_read_cmd(dev, AX_CMD_STATMNGSTS_REG, 0, 0, 1, &chipcode, 0);
+	ret = asix_read_cmd(dev, AX_CMD_STATMNGSTS_REG, 0, 0, 1, &chipcode, 0);
+	if (ret < 0) {
+		netdev_dbg(dev->net, "Failed to read STATMNGSTS_REG: %d\n", ret);
+		return ret;
+	}
+
 	chipcode &= AX_CHIPCODE_MASK;
 
 	ret = (chipcode == AX_AX88772_CHIPCODE) ? ax88772_hw_reset(dev, 0) :
@@ -919,11 +924,21 @@ static int ax88178_reset(struct usbnet *dev)
 	int gpio0 = 0;
 	u32 phyid;
 
-	asix_read_cmd(dev, AX_CMD_READ_GPIOS, 0, 0, 1, &status, 0);
+	ret = asix_read_cmd(dev, AX_CMD_READ_GPIOS, 0, 0, 1, &status, 0);
+	if (ret < 0) {
+		netdev_dbg(dev->net, "Failed to read GPIOS: %d\n", ret);
+		return ret;
+	}
+
 	netdev_dbg(dev->net, "GPIO Status: 0x%04x\n", status);
 
 	asix_write_cmd(dev, AX_CMD_WRITE_ENABLE, 0, 0, 0, NULL, 0);
-	asix_read_cmd(dev, AX_CMD_READ_EEPROM, 0x0017, 0, 2, &eeprom, 0);
+	ret = asix_read_cmd(dev, AX_CMD_READ_EEPROM, 0x0017, 0, 2, &eeprom, 0);
+	if (ret < 0) {
+		netdev_dbg(dev->net, "Failed to read EEPROM: %d\n", ret);
+		return ret;
+	}
+
 	asix_write_cmd(dev, AX_CMD_WRITE_DISABLE, 0, 0, 0, NULL, 0);
 
 	netdev_dbg(dev->net, "EEPROM index 0x17 is 0x%04x\n", eeprom);
-- 
2.34.1