Patch "drm/dp/mst: make mst i2c transfer code more robust." has been added to the 4.1-stable tree

Patch "drm/dp/mst: make mst i2c transfer code more robust." has been added to the 4.1-stable tree

[gregkh]

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 4.1-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-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From ae491542cbbbcca0ec8938c37d4079a985e58440 Mon Sep 17 00:00:00 2001
From: Dave Airlie <airlied@gmail.com>
Date: Wed, 14 Oct 2015 18:51:17 +1000
Subject: drm/dp/mst: make mst i2c transfer code more robust.

From: Dave Airlie <airlied@gmail.com>

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.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2766,12 +2766,13 @@ 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;
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -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 airlied@gmail.com are

queue-4.1/drm-dp-mst-make-mst-i2c-transfer-code-more-robust.patch