[SRU][F][PATCH v2 1/3] net: asix: fix uninit value bugs

[Koichiro Den]

From: Pavel Skripkin <paskripkin at gmail.com>

Syzbot reported uninit-value in asix_mdio_read(). The problem was in
missing error handling. asix_read_cmd() should initialize passed stack
variable smsr, but it can fail in some cases. Then while condidition
checks possibly uninit smsr variable.

Since smsr is uninitialized stack variable, driver can misbehave,
because smsr will be random in case of asix_read_cmd() failure.
Fix it by adding error handling and just continue the loop instead of
checking uninit value.

Added helper function for checking Host_En bit, since wrong loop was used
in 4 functions and there is no need in copy-pasting code parts.

Cc: Robert Foss <robert.foss at collabora.com>
Fixes: d9fe64e51114 ("net: asix: Add in_pm parameter")
Reported-by: syzbot+a631ec9e717fb0423053 at syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin at gmail.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(backported from commit a786e3195d6af183033e86f0518ffd2c51c0e8ac)
[koichiroden: Adjusted context due to missing commit d275afb66371 ("net:
usb: asix: add error handling for asix_mdio_* functions"), which in turn
depends on e532a096be0e ("net: usb: asix: ax88772: add phylib support").
Ref. [PATCH net-next v2 0/8] port asix ax88772 to the PHYlib
https://lore.kernel.org/linux-usb/20210607082727.26045-1-o.rempel@pengutronix.de/]
CVE-2021-47101
Signed-off-by: Koichiro Den <koichiro.den at canonical.com>
---
 drivers/net/usb/asix_common.c | 71 +++++++++++++++--------------------
 1 file changed, 31 insertions(+), 40 deletions(-)

diff --git a/drivers/net/usb/asix_common.c b/drivers/net/usb/asix_common.c
index 7bc6e8f856fe..12ce52600eaf 100644
--- a/drivers/net/usb/asix_common.c
+++ b/drivers/net/usb/asix_common.c
@@ -63,6 +63,29 @@ void asix_write_cmd_async(struct usbnet *dev, u8 cmd, u16 value, u16 index,
 			       value, index, data, size);
 }
 
+static int asix_check_host_enable(struct usbnet *dev, int in_pm)
+{
+	int i, ret;
+	u8 smsr;
+
+	for (i = 0; i < 30; ++i) {
+		ret = asix_set_sw_mii(dev, in_pm);
+		if (ret == -ENODEV || ret == -ETIMEDOUT)
+			break;
+		usleep_range(1000, 1100);
+		ret = asix_read_cmd(dev, AX_CMD_STATMNGSTS_REG,
+				    0, 0, 1, &smsr, in_pm);
+		if (ret == -ENODEV)
+			break;
+		else if (ret < 0)
+			continue;
+		else if (smsr & AX_HOST_EN)
+			break;
+	}
+
+	return ret;
+}
+
 static void reset_asix_rx_fixup_info(struct asix_rx_fixup_info *rx)
 {
 	/* Reset the variables that have a lifetime outside of
@@ -445,19 +468,11 @@ int asix_mdio_read(struct net_device *netdev, int phy_id, int loc)
 {
 	struct usbnet *dev = netdev_priv(netdev);
 	__le16 res;
-	u8 smsr;
-	int i = 0;
 	int ret;
 
 	mutex_lock(&dev->phy_mutex);
-	do {
-		ret = asix_set_sw_mii(dev, 0);
-		if (ret == -ENODEV || ret == -ETIMEDOUT)
-			break;
-		usleep_range(1000, 1100);
-		ret = asix_read_cmd(dev, AX_CMD_STATMNGSTS_REG,
-				    0, 0, 1, &smsr, 0);
-	} while (!(smsr & AX_HOST_EN) && (i++ < 30) && (ret != -ENODEV));
+
+	ret = asix_check_host_enable(dev, 0);
 	if (ret == -ENODEV || ret == -ETIMEDOUT) {
 		mutex_unlock(&dev->phy_mutex);
 		return ret;
@@ -478,22 +493,14 @@ void asix_mdio_write(struct net_device *netdev, int phy_id, int loc, int val)
 {
 	struct usbnet *dev = netdev_priv(netdev);
 	__le16 res = cpu_to_le16(val);
-	u8 smsr;
-	int i = 0;
 	int ret;
 
 	netdev_dbg(dev->net, "asix_mdio_write() phy_id=0x%02x, loc=0x%02x, val=0x%04x\n",
 			phy_id, loc, val);
 
 	mutex_lock(&dev->phy_mutex);
-	do {
-		ret = asix_set_sw_mii(dev, 0);
-		if (ret == -ENODEV)
-			break;
-		usleep_range(1000, 1100);
-		ret = asix_read_cmd(dev, AX_CMD_STATMNGSTS_REG,
-				    0, 0, 1, &smsr, 0);
-	} while (!(smsr & AX_HOST_EN) && (i++ < 30) && (ret != -ENODEV));
+
+	ret = asix_check_host_enable(dev, 0);
 	if (ret == -ENODEV) {
 		mutex_unlock(&dev->phy_mutex);
 		return;
@@ -509,19 +516,11 @@ int asix_mdio_read_nopm(struct net_device *netdev, int phy_id, int loc)
 {
 	struct usbnet *dev = netdev_priv(netdev);
 	__le16 res;
-	u8 smsr;
-	int i = 0;
 	int ret;
 
 	mutex_lock(&dev->phy_mutex);
-	do {
-		ret = asix_set_sw_mii(dev, 1);
-		if (ret == -ENODEV || ret == -ETIMEDOUT)
-			break;
-		usleep_range(1000, 1100);
-		ret = asix_read_cmd(dev, AX_CMD_STATMNGSTS_REG,
-				    0, 0, 1, &smsr, 1);
-	} while (!(smsr & AX_HOST_EN) && (i++ < 30) && (ret != -ENODEV));
+
+	ret = asix_check_host_enable(dev, 1);
 	if (ret == -ENODEV || ret == -ETIMEDOUT) {
 		mutex_unlock(&dev->phy_mutex);
 		return ret;
@@ -543,22 +542,14 @@ asix_mdio_write_nopm(struct net_device *netdev, int phy_id, int loc, int val)
 {
 	struct usbnet *dev = netdev_priv(netdev);
 	__le16 res = cpu_to_le16(val);
-	u8 smsr;
-	int i = 0;
 	int ret;
 
 	netdev_dbg(dev->net, "asix_mdio_write() phy_id=0x%02x, loc=0x%02x, val=0x%04x\n",
 			phy_id, loc, val);
 
 	mutex_lock(&dev->phy_mutex);
-	do {
-		ret = asix_set_sw_mii(dev, 1);
-		if (ret == -ENODEV)
-			break;
-		usleep_range(1000, 1100);
-		ret = asix_read_cmd(dev, AX_CMD_STATMNGSTS_REG,
-				    0, 0, 1, &smsr, 1);
-	} while (!(smsr & AX_HOST_EN) && (i++ < 30) && (ret != -ENODEV));
+
+	ret = asix_check_host_enable(dev, 1);
 	if (ret == -ENODEV) {
 		mutex_unlock(&dev->phy_mutex);
 		return;
-- 
2.43.0