[PATCH 1/4] net: fix uninitialised access in mii_nway_restart()

[PATCH 1/4] net: fix uninitialised access in mii_nway_restart()

[Qasim Ijaz]

In mii_nway_restart() during the line:

        bmcr = mii->mdio_read(mii->dev, mii->phy_id, MII_BMCR);

The code attempts to call mii->mdio_read which is ch9200_mdio_read().

ch9200_mdio_read() utilises a local buffer, which is initialised
with control_read():

        unsigned char buff[2];

However buff is conditionally initialised inside control_read():

        if (err == size) {
                memcpy(data, buf, size);
        }

If the condition of "err == size" is not met, then buff remains
uninitialised. Once this happens the uninitialised buff is accessed
and returned during ch9200_mdio_read():

        return (buff[0] | buff[1] << 8);

The problem stems from the fact that ch9200_mdio_read() ignores the
return value of control_read(), leading to uinit-access of buff.

To fix this we should check the return value of control_read()
and return early on error.

Reported-by: syzbot <syzbot+3361c2d6f78a3e0892f9@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=3361c2d6f78a3e0892f9
Tested-by: syzbot <syzbot+3361c2d6f78a3e0892f9@syzkaller.appspotmail.com>
Fixes: 4a476bd6d1d9 ("usbnet: New driver for QinHeng CH9200 devices")
Cc: stable@vger.kernel.org
Signed-off-by: Qasim Ijaz <qasdev00@gmail.com>
---
 drivers/net/mii.c        | 2 ++
 drivers/net/usb/ch9200.c | 7 +++++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/mii.c b/drivers/net/mii.c
index 37bc3131d31a..e305bf0f1d04 100644
--- a/drivers/net/mii.c
+++ b/drivers/net/mii.c
@@ -464,6 +464,8 @@ int mii_nway_restart (struct mii_if_info *mii)
 
 	/* if autoneg is off, it's an error */
 	bmcr = mii->mdio_read(mii->dev, mii->phy_id, MII_BMCR);
+	if (bmcr < 0)
+		return bmcr;
 
 	if (bmcr & BMCR_ANENABLE) {
 		bmcr |= BMCR_ANRESTART;
diff --git a/drivers/net/usb/ch9200.c b/drivers/net/usb/ch9200.c
index f69d9b902da0..a206ffa76f1b 100644
--- a/drivers/net/usb/ch9200.c
+++ b/drivers/net/usb/ch9200.c
@@ -178,6 +178,7 @@ static int ch9200_mdio_read(struct net_device *netdev, int phy_id, int loc)
 {
 	struct usbnet *dev = netdev_priv(netdev);
 	unsigned char buff[2];
+	int ret;
 
 	netdev_dbg(netdev, "%s phy_id:%02x loc:%02x\n",
 		   __func__, phy_id, loc);
@@ -185,8 +186,10 @@ static int ch9200_mdio_read(struct net_device *netdev, int phy_id, int loc)
 	if (phy_id != 0)
 		return -ENODEV;
 
-	control_read(dev, REQUEST_READ, 0, loc * 2, buff, 0x02,
-		     CONTROL_TIMEOUT_MS);
+	ret = control_read(dev, REQUEST_READ, 0, loc * 2, buff, 0x02,
+			   CONTROL_TIMEOUT_MS);
+	if (ret < 0)
+		return ret;
 
 	return (buff[0] | buff[1] << 8);
 }
-- 
2.39.5

[PATCH 1/4] net: fix uninitialised access in mii_nway_restart()

[Qasim Ijaz]

In mii_nway_restart() during the line:

        bmcr = mii->mdio_read(mii->dev, mii->phy_id, MII_BMCR);

The code attempts to call mii->mdio_read which is ch9200_mdio_read().

ch9200_mdio_read() utilises a local buffer, which is initialised
with control_read():

        unsigned char buff[2];

However buff is conditionally initialised inside control_read():

        if (err == size) {
                memcpy(data, buf, size);
        }

If the condition of "err == size" is not met, then buff remains
uninitialised. Once this happens the uninitialised buff is accessed
and returned during ch9200_mdio_read():

        return (buff[0] | buff[1] << 8);

The problem stems from the fact that ch9200_mdio_read() ignores the
return value of control_read(), leading to uinit-access of buff.

To fix this we should check the return value of control_read()
and return early on error.

Reported-by: syzbot <syzbot+3361c2d6f78a3e0892f9@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=3361c2d6f78a3e0892f9
Tested-by: syzbot <syzbot+3361c2d6f78a3e0892f9@syzkaller.appspotmail.com>
Fixes: 4a476bd6d1d9 ("usbnet: New driver for QinHeng CH9200 devices")
Cc: stable@vger.kernel.org
Signed-off-by: Qasim Ijaz <qasdev00@gmail.com>
---
 drivers/net/mii.c        | 2 ++
 drivers/net/usb/ch9200.c | 7 +++++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/mii.c b/drivers/net/mii.c
index 37bc3131d31a..e305bf0f1d04 100644
--- a/drivers/net/mii.c
+++ b/drivers/net/mii.c
@@ -464,6 +464,8 @@ int mii_nway_restart (struct mii_if_info *mii)
 
 	/* if autoneg is off, it's an error */
 	bmcr = mii->mdio_read(mii->dev, mii->phy_id, MII_BMCR);
+	if (bmcr < 0)
+		return bmcr;
 
 	if (bmcr & BMCR_ANENABLE) {
 		bmcr |= BMCR_ANRESTART;
diff --git a/drivers/net/usb/ch9200.c b/drivers/net/usb/ch9200.c
index f69d9b902da0..a206ffa76f1b 100644
--- a/drivers/net/usb/ch9200.c
+++ b/drivers/net/usb/ch9200.c
@@ -178,6 +178,7 @@ static int ch9200_mdio_read(struct net_device *netdev, int phy_id, int loc)
 {
 	struct usbnet *dev = netdev_priv(netdev);
 	unsigned char buff[2];
+	int ret;
 
 	netdev_dbg(netdev, "%s phy_id:%02x loc:%02x\n",
 		   __func__, phy_id, loc);
@@ -185,8 +186,10 @@ static int ch9200_mdio_read(struct net_device *netdev, int phy_id, int loc)
 	if (phy_id != 0)
 		return -ENODEV;
 
-	control_read(dev, REQUEST_READ, 0, loc * 2, buff, 0x02,
-		     CONTROL_TIMEOUT_MS);
+	ret = control_read(dev, REQUEST_READ, 0, loc * 2, buff, 0x02,
+			   CONTROL_TIMEOUT_MS);
+	if (ret < 0)
+		return ret;
 
 	return (buff[0] | buff[1] << 8);
 }
-- 
2.39.5

[PATCH 1/4] net: fix uninitialised access in mii_nway_restart()

[Qasim Ijaz]

In mii_nway_restart() during the line:

        bmcr = mii->mdio_read(mii->dev, mii->phy_id, MII_BMCR);

The code attempts to call mii->mdio_read which is ch9200_mdio_read().

ch9200_mdio_read() utilises a local buffer, which is initialised
with control_read():

        unsigned char buff[2];

However buff is conditionally initialised inside control_read():

        if (err == size) {
                memcpy(data, buf, size);
        }

If the condition of "err == size" is not met, then buff remains
uninitialised. Once this happens the uninitialised buff is accessed
and returned during ch9200_mdio_read():

        return (buff[0] | buff[1] << 8);

The problem stems from the fact that ch9200_mdio_read() ignores the
return value of control_read(), leading to uinit-access of buff.

To fix this we should check the return value of control_read()
and return early on error.

Reported-by: syzbot <syzbot+3361c2d6f78a3e0892f9@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=3361c2d6f78a3e0892f9
Tested-by: syzbot <syzbot+3361c2d6f78a3e0892f9@syzkaller.appspotmail.com>
Fixes: 4a476bd6d1d9 ("usbnet: New driver for QinHeng CH9200 devices")
Cc: stable@vger.kernel.org
Signed-off-by: Qasim Ijaz <qasdev00@gmail.com>
---
 drivers/net/mii.c        | 2 ++
 drivers/net/usb/ch9200.c | 7 +++++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/mii.c b/drivers/net/mii.c
index 37bc3131d31a..e305bf0f1d04 100644
--- a/drivers/net/mii.c
+++ b/drivers/net/mii.c
@@ -464,6 +464,8 @@ int mii_nway_restart (struct mii_if_info *mii)
 
 	/* if autoneg is off, it's an error */
 	bmcr = mii->mdio_read(mii->dev, mii->phy_id, MII_BMCR);
+	if (bmcr < 0)
+		return bmcr;
 
 	if (bmcr & BMCR_ANENABLE) {
 		bmcr |= BMCR_ANRESTART;
diff --git a/drivers/net/usb/ch9200.c b/drivers/net/usb/ch9200.c
index f69d9b902da0..a206ffa76f1b 100644
--- a/drivers/net/usb/ch9200.c
+++ b/drivers/net/usb/ch9200.c
@@ -178,6 +178,7 @@ static int ch9200_mdio_read(struct net_device *netdev, int phy_id, int loc)
 {
 	struct usbnet *dev = netdev_priv(netdev);
 	unsigned char buff[2];
+	int ret;
 
 	netdev_dbg(netdev, "%s phy_id:%02x loc:%02x\n",
 		   __func__, phy_id, loc);
@@ -185,8 +186,10 @@ static int ch9200_mdio_read(struct net_device *netdev, int phy_id, int loc)
 	if (phy_id != 0)
 		return -ENODEV;
 
-	control_read(dev, REQUEST_READ, 0, loc * 2, buff, 0x02,
-		     CONTROL_TIMEOUT_MS);
+	ret = control_read(dev, REQUEST_READ, 0, loc * 2, buff, 0x02,
+			   CONTROL_TIMEOUT_MS);
+	if (ret < 0)
+		return ret;
 
 	return (buff[0] | buff[1] << 8);
 }
-- 
2.39.5

Re: [PATCH 1/4] net: fix uninitialised access in mii_nway_restart()

[Simon Horman]

On Wed, Mar 19, 2025 at 11:21:53AM +0000, Qasim Ijaz wrote:
> In mii_nway_restart() during the line:
> 
>         bmcr = mii->mdio_read(mii->dev, mii->phy_id, MII_BMCR);
> 
> The code attempts to call mii->mdio_read which is ch9200_mdio_read().
> 
> ch9200_mdio_read() utilises a local buffer, which is initialised
> with control_read():
> 
>         unsigned char buff[2];
> 
> However buff is conditionally initialised inside control_read():
> 
>         if (err == size) {
>                 memcpy(data, buf, size);
>         }
> 
> If the condition of "err == size" is not met, then buff remains
> uninitialised. Once this happens the uninitialised buff is accessed
> and returned during ch9200_mdio_read():
> 
>         return (buff[0] | buff[1] << 8);
> 
> The problem stems from the fact that ch9200_mdio_read() ignores the
> return value of control_read(), leading to uinit-access of buff.
> 
> To fix this we should check the return value of control_read()
> and return early on error.
> 
> Reported-by: syzbot <syzbot+3361c2d6f78a3e0892f9@syzkaller.appspotmail.com>
> Closes: https://syzkaller.appspot.com/bug?extid=3361c2d6f78a3e0892f9
> Tested-by: syzbot <syzbot+3361c2d6f78a3e0892f9@syzkaller.appspotmail.com>
> Fixes: 4a476bd6d1d9 ("usbnet: New driver for QinHeng CH9200 devices")
> Cc: stable@vger.kernel.org
> Signed-off-by: Qasim Ijaz <qasdev00@gmail.com>

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH 1/4] net: fix uninitialised access in mii_nway_restart()

[Jakub Kicinski]

On Wed, 19 Mar 2025 11:21:53 +0000 Qasim Ijaz wrote:
> --- a/drivers/net/mii.c
> +++ b/drivers/net/mii.c
> @@ -464,6 +464,8 @@ int mii_nway_restart (struct mii_if_info *mii)
>  
>  	/* if autoneg is off, it's an error */
>  	bmcr = mii->mdio_read(mii->dev, mii->phy_id, MII_BMCR);
> +	if (bmcr < 0)
> +		return bmcr;
>  
>  	if (bmcr & BMCR_ANENABLE) {
>  		bmcr |= BMCR_ANRESTART;

We error check just one mdio_read() but there's a whole bunch of them
in this file. What's the expected behavior then? Are all of them buggy?

This patch should be split into core and driver parts.
-- 
pw-bot: cr