Hi Peter, On 09.10.23 22:48, Peter Korsgaard wrote: > > > 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 or if no data is read (see > > __usbnet_read_cmd()). 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 returning an error if the read operation failed or no data was read. > > > [1] https://syzkaller.appspot.com/bug?extid=1f53a30781af65d2c955 > > > Signed-off-by: Javier Carrasco <javier.carrasco.cruz@xxxxxxxxx> > > Reported-and-tested-by: syzbot+1f53a30781af65d2c955@xxxxxxxxxxxxxxxxxxxxxxxxx > > --- > > drivers/net/usb/dm9601.c | 9 ++++++++- > > 1 file changed, 8 insertions(+), 1 deletion(-) > > > diff --git a/drivers/net/usb/dm9601.c b/drivers/net/usb/dm9601.c > > index 48d7d278631e..e223daa93229 100644 > > --- a/drivers/net/usb/dm9601.c > > +++ b/drivers/net/usb/dm9601.c > > @@ -222,13 +222,20 @@ 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) { > > + if (err == 0) > > + err = -ENODATA; > > Looking at dm_read(), it doesn't look like we can end up here with err > == 0, but OK.You are right, I just simulated the err = 0 value from __usbnet_read_cmd() and in this case it is harmless because dm_read is called with length != 0 (in dm_read_shared_word either 1 or 2) and therefore it returns -EINVAL. A silly case where this would fail would be if length == 0, which would be wrong anyways. So I will remove the err == 0 case for v2. Thanks a lot for your feedback. > Acked-by: Peter Korsgaard <peter@xxxxxxxxxxxxx> > Best regards, Javier Carrasco
