On Tue, Feb 18, 2025 at 02:10:08AM +0100, Andrew Lunn wrote:
On Tue, Feb 18, 2025 at 12:24:43AM +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.
What about get_mac_address()?
If you find a bug, it is a good idea to look around and see if there are any more instances of the same bug. I could be wrong, but it seems like get_mac_address() suffers from the same problem?
Thank you for the feedback Andrew. I checked get_mac_address() before sending this patch and to me it looks like it does check the return value of control_read(). It accumulates the return value of each control_read() call into rd_mac_len and then checks if it not equal to what is expected (ETH_ALEN which is 6), I believe each call should return 2.
Andrew