Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 732E2C44791
From:   Bhaumik Bhatt <bbhatt@codeaurora.org>
To:     manivannan.sadhasivam@linaro.org
Cc:     linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org,
        hemantk@codeaurora.org, jhugo@codeaurora.org,
        Bhaumik Bhatt <bbhatt@codeaurora.org>
Subject: [PATCH v7 4/8] bus: mhi: core: Read transfer length from an event properly
Date:   Fri,  8 May 2020 19:26:44 -0700
Message-Id: <1588991208-26928-5-git-send-email-bbhatt@codeaurora.org>
In-Reply-To: <1588991208-26928-1-git-send-email-bbhatt@codeaurora.org>
References: <1588991208-26928-1-git-send-email-bbhatt@codeaurora.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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 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 <hemantk@codeaurora.org>
Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: Jeffrey Hugo <jhugo@codeaurora.org>
---
 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 30798ec..6a80666 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