[PATCH] video: exynos: fix build warning and bad pointer deref in dp driver

I'm not 100% sure if the fix for 'adjust_request' is correct, since
it's uncertain what the original intent was. But it's so clearly an
uninitialized pointer dereference that my resolution seems to make sense.

drivers/video/exynos/exynos_dp_core.c: In function 'exynos_dp_set_link_train':
drivers/video/exynos/exynos_dp_core.c:521:21: warning: 'adjust_request' may be used uninitialized in this function [-Wuninitialized]
drivers/video/exynos/exynos_dp_core.c:481:6: note: 'adjust_request' was declared here
drivers/video/exynos/exynos_dp_core.c:529:18: warning: 'reg' may be used uninitialized in this function [-Wuninitialized]
drivers/video/exynos/exynos_dp_core.c:395:6: note: 'reg' was declared here

Signed-off-by: Olof Johansson <redacted>
---
 drivers/video/exynos/exynos_dp_core.c |   23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/drivers/video/exynos/exynos_dp_core.c b/drivers/video/exynos/exynos_dp_core.c
index 2a4481c..8973e18 100644
--- a/drivers/video/exynos/exynos_dp_core.c
+++ b/drivers/video/exynos/exynos_dp_core.c

@@ -392,24 +392,19 @@ static unsigned int exynos_dp_get_lane_link_training(
 				struct exynos_dp_device *dp,
 				int lane)
 {
-	u32 reg;
-
 	switch (lane) {
 	case 0:
-		reg = exynos_dp_get_lane0_link_training(dp);
-		break;
+		return exynos_dp_get_lane0_link_training(dp);
 	case 1:
-		reg = exynos_dp_get_lane1_link_training(dp);
-		break;
+		return exynos_dp_get_lane1_link_training(dp);
 	case 2:
-		reg = exynos_dp_get_lane2_link_training(dp);
-		break;
+		return exynos_dp_get_lane2_link_training(dp);
 	case 3:
-		reg = exynos_dp_get_lane3_link_training(dp);
-		break;
+		return exynos_dp_get_lane3_link_training(dp);
 	}
 
-	return reg;
+	WARN_ON(1);
+	return 0;
 }
 
 static void exynos_dp_reduce_link_rate(struct exynos_dp_device *dp)

@@ -489,13 +484,13 @@ static int exynos_dp_process_clock_recovery(struct exynos_dp_device *dp)
 				6, link_status);
 	lane_count = dp->link_train.lane_count;
 
+	adjust_request = link_status + (DPCD_ADDR_ADJUST_REQUEST_LANE0_1
+					- DPCD_ADDR_LANE0_1_STATUS);
+
 	if (exynos_dp_clock_recovery_ok(link_status, lane_count) = 0) {
 		/* set training pattern 2 for EQ */
 		exynos_dp_set_training_pattern(dp, TRAINING_PTN2);
 
-		adjust_request = link_status + (DPCD_ADDR_ADJUST_REQUEST_LANE0_1
-						- DPCD_ADDR_LANE0_1_STATUS);
-
 		exynos_dp_get_adjust_train(dp, adjust_request);
 
 		buf[0] = DPCD_SCRAMBLING_DISABLED |

-- 
1.7.9.2.359.gebfc2

I don't like multi return.

It makes the problem. adjust_request will be different.

OK, I understand what you want to do.
I will send the version 2 patch which is simpler.

Thank you for sending the patch.

 	if (exynos_dp_clock_recovery_ok(link_status, lane_count) = 0) {
 		/* set training pattern 2 for EQ */
 		exynos_dp_set_training_pattern(dp, TRAINING_PTN2);

-		adjust_request = link_status + (DPCD_ADDR_ADJUST_REQUEST_LANE0_1
-						- DPCD_ADDR_LANE0_1_STATUS);
-
 		exynos_dp_get_adjust_train(dp, adjust_request);

 		buf[0] = DPCD_SCRAMBLING_DISABLED |
--
1.7.9.2.359.gebfc2

-----Original Message-----
From: Olof Johansson [mailto:olof@lixom.net]
Sent: Monday, April 09, 2012 1:16 PM

I'm not 100% sure if the fix for 'adjust_request' is correct, since
it's uncertain what the original intent was. But it's so clearly an
uninitialized pointer dereference that my resolution seems to make sense.

drivers/video/exynos/exynos_dp_core.c: In function 'exynos_dp_set_link_train':
drivers/video/exynos/exynos_dp_core.c:521:21: warning: 'adjust_request' may be used uninitialized in
this function [-Wuninitialized]
drivers/video/exynos/exynos_dp_core.c:481:6: note: 'adjust_request' was declared here
drivers/video/exynos/exynos_dp_core.c:529:18: warning: 'reg' may be used uninitialized in this function
[-Wuninitialized]
drivers/video/exynos/exynos_dp_core.c:395:6: note: 'reg' was declared here

My compiler cannot detect this warning.
What is your compiler version?

On Mon, Apr 9, 2012 at 1:46 AM, Jingoo Han [off-list ref] wrote:

quoted

-----Original Message-----
From: Olof Johansson [mailto:olof@lixom.net]
Sent: Monday, April 09, 2012 1:16 PM

I'm not 100% sure if the fix for 'adjust_request' is correct, since
it's uncertain what the original intent was. But it's so clearly an
uninitialized pointer dereference that my resolution seems to make sense.

drivers/video/exynos/exynos_dp_core.c: In function 'exynos_dp_set_link_train':
drivers/video/exynos/exynos_dp_core.c:521:21: warning: 'adjust_request' may be used uninitialized in
this function [-Wuninitialized]
drivers/video/exynos/exynos_dp_core.c:481:6: note: 'adjust_request' was declared here
drivers/video/exynos/exynos_dp_core.c:529:18: warning: 'reg' may be used uninitialized in this function
[-Wuninitialized]
drivers/video/exynos/exynos_dp_core.c:395:6: note: 'reg' was declared here

Signed-off-by: Olof Johansson <redacted>
---
 drivers/video/exynos/exynos_dp_core.c |   23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/drivers/video/exynos/exynos_dp_core.c b/drivers/video/exynos/exynos_dp_core.c
index 2a4481c..8973e18 100644
--- a/drivers/video/exynos/exynos_dp_core.c
+++ b/drivers/video/exynos/exynos_dp_core.c

@@ -392,24 +392,19 @@ static unsigned int exynos_dp_get_lane_link_training(

                              struct exynos_dp_device *dp,
                              int lane)
 {
-     u32 reg;
-
      switch (lane) {
      case 0:
-             reg = exynos_dp_get_lane0_link_training(dp);
-             break;
+             return exynos_dp_get_lane0_link_training(dp);
      case 1:
-             reg = exynos_dp_get_lane1_link_training(dp);
-             break;
+             return exynos_dp_get_lane1_link_training(dp);
      case 2:
-             reg = exynos_dp_get_lane2_link_training(dp);
-             break;
+             return exynos_dp_get_lane2_link_training(dp);
      case 3:
-             reg = exynos_dp_get_lane3_link_training(dp);
-             break;
+             return exynos_dp_get_lane3_link_training(dp);
      }

I don't like multi return.

In a small helper function like this there's nothing wrong with it.
Larger functions? Sure.

Adding a default in the switch didn't seem like an improvement to me.
But I'll leave it up to you.

quoted

-     return reg;
+     WARN_ON(1);
+     return 0;
 }

 static void exynos_dp_reduce_link_rate(struct exynos_dp_device *dp)

@@ -489,13 +484,13 @@ static int exynos_dp_process_clock_recovery(struct exynos_dp_device *dp)

                              6, link_status);
      lane_count = dp->link_train.lane_count;

+     adjust_request = link_status + (DPCD_ADDR_ADJUST_REQUEST_LANE0_1
+                                     - DPCD_ADDR_LANE0_1_STATUS);
+

It makes the problem. adjust_request will be different.

OK, I understand what you want to do.
I will send the version 2 patch which is simpler.

Thank you for sending the patch.

Ok, thanks. As I said, I'm not sure what your intent with the second
(else) code path was.


-Olof

On Mon, Apr 9, 2012 at 2:25 AM, Jingoo Han [off-list ref] wrote:

quoted

-----Original Message-----
From: Olof Johansson [mailto:olof@lixom.net]
Sent: Monday, April 09, 2012 1:16 PM

I'm not 100% sure if the fix for 'adjust_request' is correct, since
it's uncertain what the original intent was. But it's so clearly an
uninitialized pointer dereference that my resolution seems to make sense.

drivers/video/exynos/exynos_dp_core.c: In function 'exynos_dp_set_link_train':
drivers/video/exynos/exynos_dp_core.c:521:21: warning: 'adjust_request' may be used uninitialized in
this function [-Wuninitialized]
drivers/video/exynos/exynos_dp_core.c:481:6: note: 'adjust_request' was declared here
drivers/video/exynos/exynos_dp_core.c:529:18: warning: 'reg' may be used uninitialized in this function
[-Wuninitialized]
drivers/video/exynos/exynos_dp_core.c:395:6: note: 'reg' was declared here

My compiler cannot detect this warning.
What is your compiler version?

gcc version 4.6.2 (GCC)


-Olof