On Fri, Apr 15, 2022 at 05:47:05PM +0800, Wang Cheng wrote:
> Hi Dan, thx for your review.
>
> On 22/04/14 06:42PM, Dan Carpenter wrote:
> > On Thu, Apr 14, 2022 at 10:12:23PM +0800, Wang Cheng wrote:
> > > Due to the case that "requesttype == 0x01 && status <= 0"
> > > isn't handled in r8712_usbctrl_vendorreq(),
> > > "data" (drivers/staging/rtl8712/usb_ops.c:32)
> > > will be returned without initialization.
> > >
> > > When "tmpU1b" (drivers/staging/rtl8712/usb_intf.c:395)
> > > is 0, mac[6] (usb_intf.c:394) won't be initialized,
> > > which leads to accessing uninit-value on usb_intf.c:541.
> >
> > These line numbers are sort of useless because everyone is on a
> > different git hash.
>
> I will correct this.
>
> >
> > >
> > > Reported-and-tested-by: syzbot+6f5ecd144854c0d8580b@xxxxxxxxxxxxxxxxxxxxxxxxx
> > > Signed-off-by: Wang Cheng <wanngchenng@xxxxxxxxx>
> > > ---
> > > drivers/staging/rtl8712/usb_intf.c | 6 +++---
> > > drivers/staging/rtl8712/usb_ops_linux.c | 14 ++++++++------
> > > 2 files changed, 11 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/drivers/staging/rtl8712/usb_intf.c b/drivers/staging/rtl8712/usb_intf.c
> > > index ee4c61f85a07..50dcd3ecb685 100644
> > > --- a/drivers/staging/rtl8712/usb_intf.c
> > > +++ b/drivers/staging/rtl8712/usb_intf.c
> > > @@ -538,13 +538,13 @@ static int r871xu_drv_init(struct usb_interface *pusb_intf,
> > > } else {
> > > AutoloadFail = false;
> > > }
> > > - if (((mac[0] == 0xff) && (mac[1] == 0xff) &&
> > > + if ((!AutoloadFail) ||
> > > + ((mac[0] == 0xff) && (mac[1] == 0xff) &&
> > > (mac[2] == 0xff) && (mac[3] == 0xff) &&
> > > (mac[4] == 0xff) && (mac[5] == 0xff)) ||
> > > ((mac[0] == 0x00) && (mac[1] == 0x00) &&
> > > (mac[2] == 0x00) && (mac[3] == 0x00) &&
> > > - (mac[4] == 0x00) && (mac[5] == 0x00)) ||
> > > - (!AutoloadFail)) {
> > > + (mac[4] == 0x00) && (mac[5] == 0x00))) {
> > > mac[0] = 0x00;
> > > mac[1] = 0xe0;
> > > mac[2] = 0x4c;
> >
> > This is a separate fix from the rest of the patch. Send it by itself.
>
> Ah, thought to send a patch series.
>
Yes, please. Send two patches.
> >
> >
> > > diff --git a/drivers/staging/rtl8712/usb_ops_linux.c b/drivers/staging/rtl8712/usb_ops_linux.c
> > > index f984a5ab2c6f..e321ca4453ca 100644
> > > --- a/drivers/staging/rtl8712/usb_ops_linux.c
> > > +++ b/drivers/staging/rtl8712/usb_ops_linux.c
> > > @@ -495,12 +495,14 @@ int r8712_usbctrl_vendorreq(struct intf_priv *pintfpriv, u8 request, u16 value,
> > > }
> > > status = usb_control_msg(udev, pipe, request, reqtype, value, index,
> > > pIo_buf, len, 500);
> > > - if (status > 0) { /* Success this control transfer. */
> > > - if (requesttype == 0x01) {
> > > - /* For Control read transfer, we have to copy the read
> > > - * data from pIo_buf to pdata.
> > > - */
> > > - memcpy(pdata, pIo_buf, status);
> > > + /* For Control read transfer, copy the read data from pIo_buf to pdata
> > > + * when control transfer success; otherwise init *pdata with 0.
> > > + */
> > > + if (requesttype == 0x01) {
> > > + if (status > 0)
> > > + memcpy(pdata, pIo_buf, status);
> > > + else
> > > + *(u32 *)pdata = 0;
> > > }
> >
> > This isn't really correct. In many cases status is "len" is less than 4.
> > I'm slightly surprised that nothing complains about that as an
> > uninitialized access. But then another problem is that "status" can be
> > less than "len".
>
> Sorry, I should explain it clearly. If I did right, watching "status"
> with gdb while running syzkaller reproducer, "status" returns from
> usb_control_msg() is -71. In which case, *pdata won't be touched in
> r8712_usbctrl_vendorreq(). As a result, "data" in
> usb_read8()/usb_read16()/usb_read32() will be returned without
> initialization. I think that is why kmsan reports:
> Local variable data created at:
> usb_read8+0x5d/0x130 drivers/staging/rtl8712/usb_ops.c:33
> r8712_read8+0xa5/0xd0 drivers/staging/rtl8712/rtl8712_io.c:29
Yes. I understood that.
>
> >
> > A better fix instead of setting pdata to zero would be to add error
> > checking in the callers and then change this code to use
> > usb_control_msg_send/recv(). Probably just initialize "data" in the
> > callers as well.
>
> I tried something similar which also works fine, but I think this patch
> does't fix it at root.
> https://syzkaller.appspot.com/text?tag=Patch&x=15be2970f00000
>
Ugh... Sorry, I had not looked closely at usb_read8() and friends.
(This code is all so terrible). Ideally they would have some way to
return errors. Oh well. Anyway, I guess do like this:
status = r8712_usbctrl_vendorreq(intfpriv, request, wvalue, index,
&data, len, requesttype);
if (status < 0)
return 0;
return (u8)(le32_to_cpu(data) & 0x0ff);
But in r8712_usbctrl_vendorreq() you really need to make the other
changes I mentioned as well. If you want to do it as a separate patch
that's fine too.
if (status < 0)
return status;
if (status != len)
return -EREMOTEIO;
if (reqtype == 0x1)
memcpy();
return 0;
regards,
dan carpenter
