linux-kernel - [PATCH 4.4 77/83] drm/mst: Fix error handling during MST sideband message reception

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Message-Id: <20170725191720.464807812@linuxfoundation.org>
Date:   Tue, 25 Jul 2017 12:19:41 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dave Airlie <airlied@...hat.com>,
        Lyude <lyude@...hat.com>, Daniel Vetter <daniel.vetter@...ll.ch>,
        Imre Deak <imre.deak@...el.com>
Subject: [PATCH 4.4 77/83] drm/mst: Fix error handling during MST sideband message reception

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Imre Deak <imre.deak@...el.com>

commit 448421b5e93b9177c5698f0cf6f5e72d2995eeca upstream.

Handle any error due to partial reads, timeouts etc. to avoid parsing
uninitialized data subsequently. Also bail out if the parsing itself
fails.

Cc: Dave Airlie <airlied@...hat.com>
Cc: Lyude <lyude@...hat.com>
Cc: Daniel Vetter <daniel.vetter@...ll.ch>
Signed-off-by: Imre Deak <imre.deak@...el.com>
Reviewed-by: Lyude <lyude@...hat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20170719114330.26540-2-imre.deak@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/drm_dp_mst_topology.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2195,11 +2195,17 @@ static void drm_dp_get_one_sb_msg(struct
 		ret = drm_dp_dpcd_read(mgr->aux, basereg + curreply,
 				    replyblock, len);
 		if (ret != len) {
-			DRM_DEBUG_KMS("failed to read a chunk\n");
+			DRM_DEBUG_KMS("failed to read a chunk (len %d, ret %d)\n",
+				      len, ret);
+			return;
 		}
+
 		ret = drm_dp_sideband_msg_build(msg, replyblock, len, false);
-		if (ret == false)
+		if (!ret) {
 			DRM_DEBUG_KMS("failed to build sideband msg\n");
+			return;
+		}
+
 		curreply += len;
 		replylen -= len;
 	}