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); }