On Tue, Mar 11, 2025 at 04:11:57PM +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.
Furthermore the get_mac_address() function has a similar problem where it does not directly check the return value of each control_read(), instead it sums up the return values and checks them all at the end which means if any call to control_read() fails the function just continues on.
Handle this by validating the return value of each call and fail fast and early instead of continuing.
Lastly ch9200_bind() ignores the return values of multiple control_write() calls.
Validate each control_write() call to ensure it succeeds before continuing with the next call.
Hi Qasim,
I see that these problems are related, but this is quite a lot of fixes for one patch: the rule of thumb is one fix per patch. Could you consider splitting it up along those lines?
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
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diff --git a/drivers/net/usb/ch9200.c b/drivers/net/usb/ch9200.c index f69d9b902da0..e938501a1fc8 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 != 2)
return ret;
If I understand things correctly, control_read() can (only) return:
* 2: success * negative error value: a different failure mode
If so, I think it would be more idiomatic to write this as:
if (ret < 0) return ret;
This makes it easier for those reading the code to see that an error value is being returns on error.
Likewise elsewhere in this patch.
return (buff[0] | buff[1] << 8); }
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