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

Jeffrey Hugo
2020-04-28T14:50:28Z

On 4/27/2020 8:59 PM, Bhaumik Bhatt wrote:
> From: Hemant Kumar <hemantk@codeaurora.org>
>
> 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?

> 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@codeaurora.org>
> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
> ---
> drivers/bus/mhi/core/main.c | 5 ++++-
> 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,
> mhi_cntrl->unmap_single(mhi_cntrl, buf_info);
>
> result.buf_addr = buf_info->cb_buf;
> - result.bytes_xferd = xfer_len;
> +
> + /* truncate to buf len if xfer_len is larger */
> + result.bytes_xferd =
> + min_t(u16, xfer_len, buf_info->len);
> mhi_del_ring_element(mhi_cntrl, buf_ring);
> mhi_del_ring_element(mhi_cntrl, tre_ring);
> local_rp = tre_ring->rp;
>

--
Jeffrey Hugo
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.