On Fri, Jan 07, 2022 at 01:57:16AM +0300, Pavel Skripkin wrote: > Syzbot reported uninit value in mcs7830_bind(). The problem was in > missing validation check for bytes read via usbnet_read_cmd(). > > usbnet_read_cmd() internally calls usb_control_msg(), that returns > number of bytes read. Code should validate that requested number of bytes > was actually read. > > So, this patch adds missing size validation check inside > mcs7830_get_reg() to prevent uninit value bugs > > CC: Arnd Bergmann <arnd@xxxxxxxx> > Reported-and-tested-by: syzbot+003c0a286b9af5412510@xxxxxxxxxxxxxxxxxxxxxxxxx > Fixes: 2a36d7083438 ("USB: driver for mcs7830 (aka DeLOCK) USB ethernet adapter") > Signed-off-by: Pavel Skripkin <paskripkin@xxxxxxxxx> > --- > > @Arnd, I am not sure about mcs7830_get_rev() function. > > Is get_reg(22, 2) == 1 valid read? If so, I think, we should call > usbnet_read_cmd() directly here, since other callers care only about > negative error values. > > Thanks > > > --- > drivers/net/usb/mcs7830.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/usb/mcs7830.c b/drivers/net/usb/mcs7830.c > index 326cc4e749d8..fdda0616704e 100644 > --- a/drivers/net/usb/mcs7830.c > +++ b/drivers/net/usb/mcs7830.c > @@ -108,8 +108,16 @@ static const char driver_name[] = "MOSCHIP usb-ethernet driver"; > > static int mcs7830_get_reg(struct usbnet *dev, u16 index, u16 size, void *data) > { > - return usbnet_read_cmd(dev, MCS7830_RD_BREQ, MCS7830_RD_BMREQ, > - 0x0000, index, data, size); > + int ret; > + > + ret = usbnet_read_cmd(dev, MCS7830_RD_BREQ, MCS7830_RD_BMREQ, > + 0x0000, index, data, size); > + if (ret < 0) > + return ret; > + else if (ret < size) > + return -ENODATA; We have a usb core function that handles these "short reads are an error" issue. Perhaps usbnet_read_cmd() should be converted to use it instead? thanks, greg k-h