2020-05-02 02:35:05

by Bhaumik Bhatt

Subject: [PATCH v4 4/8] bus: mhi: core: Read transfer length from an event properly

From: Hemant Kumar <[email protected]>

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 driver to memory
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 <[email protected]>
Signed-off-by: Bhaumik Bhatt <[email protected]>
---
drivers/bus/mhi/core/main.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
index e60ab21..159732e 100644
--- a/drivers/bus/mhi/core/main.c
+++ b/drivers/bus/mhi/core/main.c
@@ -514,7 +514,10 @@ 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;
@@ -598,7 +601,9 @@ static int parse_rsc_event(struct mhi_controller *mhi_cntrl,

result.transaction_status = (ev_code == MHI_EV_CC_OVERFLOW) ?
-EOVERFLOW : 0;
- 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);
result.buf_addr = buf_info->cb_buf;
result.dir = mhi_chan->dir;

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

2020-05-04 14:36:53

by Jeffrey Hugo

Subject: Re: [PATCH v4 4/8] bus: mhi: core: Read transfer length from an event properly

On 5/1/2020 8:32 PM, Bhaumik Bhatt wrote:
> From: Hemant Kumar <[email protected]>
>
> 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 driver to memory
> 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 <[email protected]>
> Signed-off-by: Bhaumik Bhatt <[email protected]>

Reviewed-by: Jeffrey Hugo <[email protected]>

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