syzbot has found an uninit-value bug triggered by the dm9601 driver [1]. This error happens because the variable res is not updated if the call to dm_read_shared_word returns an error. In this particular case -EPROTO was returned and res stayed uninitialized. This can be avoided by checking the return value of dm_read_shared_word and propagating the error if the read operation failed. [1] https://syzkaller.appspot.com/bug?extid=1f53a30781af65d2c955 Signed-off-by: Javier Carrasco <javier.carrasco.cruz@xxxxxxxxx> Reported-and-tested-by: syzbot+1f53a30781af65d2c955@xxxxxxxxxxxxxxxxxxxxxxxxx --- Changes in v2: - Remove unnecessary 'err == 0' case - Link to v1: https://lore.kernel.org/r/20231009-topic-dm9601_uninit_mdio_read-v1-1-d4d775e24e3b@xxxxxxxxx --- drivers/net/usb/dm9601.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/net/usb/dm9601.c b/drivers/net/usb/dm9601.c index 48d7d278631e..99ec1d4a972d 100644 --- a/drivers/net/usb/dm9601.c +++ b/drivers/net/usb/dm9601.c @@ -222,13 +222,18 @@ static int dm9601_mdio_read(struct net_device *netdev, int phy_id, int loc) struct usbnet *dev = netdev_priv(netdev); __le16 res; + int err; if (phy_id) { netdev_dbg(dev->net, "Only internal phy supported\n"); return 0; } - dm_read_shared_word(dev, 1, loc, &res); + err = dm_read_shared_word(dev, 1, loc, &res); + if (err < 0) { + netdev_err(dev->net, "MDIO read error: %d\n", err); + return err; + } netdev_dbg(dev->net, "dm9601_mdio_read() phy_id=0x%02x, loc=0x%02x, returns=0x%04x\n", --- base-commit: 94f6f0550c625fab1f373bb86a6669b45e9748b3 change-id: 20231009-topic-dm9601_uninit_mdio_read-a15918ffbd6f Best regards, -- Javier Carrasco <javier.carrasco.cruz@xxxxxxxxx>
