[PATCH] drm/amd/display: Fix off by one in hdmi_14_process_transaction()

* [PATCH] drm/amd/display: Fix off by one in hdmi_14_process_transaction()
@ 2021-03-02 11:15 ` Dan Carpenter
  0 siblings, 0 replies; 8+ messages in thread
From: Dan Carpenter @ 2021-03-02 11:15 UTC (permalink / raw)
  To: Harry Wentland, Bhawanpreet Lakha
  Cc: Leo Li, Alex Deucher, Christian König, David Airlie,
	Daniel Vetter, Dan Carpenter, Bhawanpreet Lakha,
	Rodrigo Siqueira, Wenjing Liu, amd-gfx, dri-devel,
	kernel-janitors

The hdcp_i2c_offsets[] array did not have an entry for
HDCP_MESSAGE_ID_WRITE_CONTENT_STREAM_TYPE so it led to an off by one
read overflow.  I added an entry and copied the 0x0 value for the offset
from similar code in drivers/gpu/drm/amd/display/modules/hdcp/hdcp_ddc.c.

I also declared several of these arrays as having HDCP_MESSAGE_ID_MAX
entries.  This doesn't change the code, but it's just a belt and
suspenders approach to try future proof the code.

Fixes: 4c283fdac08a ("drm/amd/display: Add HDCP module")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
From static analysis, as mentioned in the commit message the offset
is basically an educated guess.

I reported this bug on Apr 16, 2020 but I guess we lost take of it.

 drivers/gpu/drm/amd/display/dc/hdcp/hdcp_msg.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/hdcp/hdcp_msg.c b/drivers/gpu/drm/amd/display/dc/hdcp/hdcp_msg.c
index 5e384a8a83dc..51855a2624cf 100644
--- a/drivers/gpu/drm/amd/display/dc/hdcp/hdcp_msg.c
+++ b/drivers/gpu/drm/amd/display/dc/hdcp/hdcp_msg.c
@@ -39,7 +39,7 @@
 #define HDCP14_KSV_SIZE 5
 #define HDCP14_MAX_KSV_FIFO_SIZE 127*HDCP14_KSV_SIZE
 
-static const bool hdcp_cmd_is_read[] = {
+static const bool hdcp_cmd_is_read[HDCP_MESSAGE_ID_MAX] = {
 	[HDCP_MESSAGE_ID_READ_BKSV] = true,
 	[HDCP_MESSAGE_ID_READ_RI_R0] = true,
 	[HDCP_MESSAGE_ID_READ_PJ] = true,
@@ -75,7 +75,7 @@ static const bool hdcp_cmd_is_read[] = {
 	[HDCP_MESSAGE_ID_WRITE_CONTENT_STREAM_TYPE] = false
 };
 
-static const uint8_t hdcp_i2c_offsets[] = {
+static const uint8_t hdcp_i2c_offsets[HDCP_MESSAGE_ID_MAX] = {
 	[HDCP_MESSAGE_ID_READ_BKSV] = 0x0,
 	[HDCP_MESSAGE_ID_READ_RI_R0] = 0x8,
 	[HDCP_MESSAGE_ID_READ_PJ] = 0xA,
@@ -106,7 +106,8 @@ static const uint8_t hdcp_i2c_offsets[] = {
 	[HDCP_MESSAGE_ID_WRITE_REPEATER_AUTH_SEND_ACK] = 0x60,
 	[HDCP_MESSAGE_ID_WRITE_REPEATER_AUTH_STREAM_MANAGE] = 0x60,
 	[HDCP_MESSAGE_ID_READ_REPEATER_AUTH_STREAM_READY] = 0x80,
-	[HDCP_MESSAGE_ID_READ_RXSTATUS] = 0x70
+	[HDCP_MESSAGE_ID_READ_RXSTATUS] = 0x70,
+	[HDCP_MESSAGE_ID_WRITE_CONTENT_STREAM_TYPE] = 0x0,
 };
 
 struct protection_properties {
@@ -184,7 +185,7 @@ static const struct protection_properties hdmi_14_protection = {
 	.process_transaction = hdmi_14_process_transaction
 };
 
-static const uint32_t hdcp_dpcd_addrs[] = {
+static const uint32_t hdcp_dpcd_addrs[HDCP_MESSAGE_ID_MAX] = {
 	[HDCP_MESSAGE_ID_READ_BKSV] = 0x68000,
 	[HDCP_MESSAGE_ID_READ_RI_R0] = 0x68005,
 	[HDCP_MESSAGE_ID_READ_PJ] = 0xFFFFFFFF,
-- 
2.30.1


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