Re: [PATCH v2 3/8] bus: mhi: core: Read transfer length from an event properly

[Hemant Kumar]

Hi Jeff

On 4/28/20 7:50 AM, Jeffrey Hugo wrote:
> On 4/27/2020 8:59 PM, Bhaumik Bhatt wrote:
> > From: Hemant Kumar <hemantk@xxxxxxxxxxxxxx>
> >
> > When MHI Driver receives an EOT event, it reads xfer_len from the
> > event in the last TRE. The value is under control of the MHI device
> > and never validated by Host MHI driver. The value should never be
> > larger than the real size of the buffer but a malicious device can
> > set the value 0xFFFF as maximum. This causes device to memory
>
> The device will overflow, or the driver?
Done.
> > overflow (both read or write). Fix this issue by reading minimum of
> > transfer length from event and the buffer length provided.
> >
> > Signed-off-by: Hemant Kumar <hemantk@xxxxxxxxxxxxxx>
> > Signed-off-by: Bhaumik Bhatt <bbhatt@xxxxxxxxxxxxxx>
> > ---
> > Â drivers/bus/mhi/core/main.c | 5 ++++-
> > Â 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> > index 1ccd4cc..3d468d9 100644
> > --- a/drivers/bus/mhi/core/main.c
> > +++ b/drivers/bus/mhi/core/main.c
> > @@ -521,7 +521,10 @@ static int parse_xfer_event(struct mhi_controller 
> > *mhi_cntrl,
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ mhi_cntrl->unmap_single(mhi_cntrl, buf_info);
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂ result.buf_addr = buf_info->cb_buf;
> > -ÂÂÂÂÂÂÂÂÂÂÂ result.bytes_xferd = xfer_len;
> > +
> > +ÂÂÂÂÂÂÂÂÂÂÂ /* truncate to buf len if xfer_len is larger */
> > +ÂÂÂÂÂÂÂÂÂÂÂ result.bytes_xferd =
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ min_t(u16, xfer_len, buf_info->len);
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂ mhi_del_ring_element(mhi_cntrl, buf_ring);
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂ mhi_del_ring_element(mhi_cntrl, tre_ring);
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂ local_rp = tre_ring->rp;

--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project