Patch "drm/dp/mst: make mst i2c transfer code more robust." has been added to the 4.2-stable tree

This is a note to let you know that I've just added the patch titled

drm/dp/mst: make mst i2c transfer code more robust.

to the 4.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-dp-mst-make-mst-i2c-transfer-code-more-robust.patch
and it can be found in the queue-4.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Dave Airlie <[email protected]>
Date: Wed, 14 Oct 2015 18:51:17 +1000
Subject: drm/dp/mst: make mst i2c transfer code more robust.

From: Dave Airlie <[email protected]>

commit ae491542cbbbcca0ec8938c37d4079a985e58440 upstream.

This zeroes the msg so no random stack data ends up getting sent, it also limits the function to not accepting > 4 i2c msgs.

---
 drivers/gpu/drm/drm_dp_mst_topology.c |    3 ++-
 include/drm/drm_dp_mst_helper.h       |    3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

@@ -2789,12 +2789,13 @@ static int drm_dp_mst_i2c_xfer(struct i2
 	if (msgs[num - 1].flags & I2C_M_RD)
 		reading = true;
 
-	if (!reading) {
+	if (!reading || (num - 1 > DP_REMOTE_I2C_READ_MAX_TRANSACTIONS)) {
 		DRM_DEBUG_KMS("Unsupported I2C transaction for MST device\n");
 		ret = -EIO;
 		goto out;
 	}
 
+	memset(&msg, 0, sizeof(msg));
 	msg.req_type = DP_REMOTE_I2C_READ;
 	msg.u.i2c_read.num_transactions = num - 1;
 	msg.u.i2c_read.port_number = port->port_num;

@@ -253,6 +253,7 @@ struct drm_dp_remote_dpcd_write {
 	u8 *bytes;
 };
 
+#define DP_REMOTE_I2C_READ_MAX_TRANSACTIONS 4
 struct drm_dp_remote_i2c_read {
 	u8 num_transactions;
 	u8 port_number;

@@ -262,7 +263,7 @@ struct drm_dp_remote_i2c_read {
 		u8 *bytes;
 		u8 no_stop_bit;
 		u8 i2c_transaction_delay;
-	} transactions[4];
+	} transactions[DP_REMOTE_I2C_READ_MAX_TRANSACTIONS];
 	u8 read_i2c_device_id;
 	u8 num_bytes_read;
 };

Patches currently in stable-queue which might be from [email protected] are

queue-4.2/drm-dp-mst-make-mst-i2c-transfer-code-more-robust.patch