From: Shirish S <shirish.s@amd.com>
Date: Mon, 20 Nov 2017 10:37:08 +0530
Subject: drm/amd/display: check plane state before validating fbc
Git-commit: 93984bbc70b3f321b8f6a3ec303e31b084e54230
Patch-mainline: v4.15-rc2
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

While validation fbc, array_mode of the pipe is accessed
without checking plane_state exists for it.
Causing to null pointer dereferencing followed by
reboot when a crtc associated with external display(not
connected) is page flipped.

This patch adds a check for plane_state before using
it to validate fbc.

Signed-off-by: Shirish S <shirish.s@amd.com>
Reviewed-by: Roman Li <Roman.Li@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c
+++ b/drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c
@@ -1774,6 +1774,10 @@ static enum dc_status validate_fbc(struc
 	if (pipe_ctx->stream->sink->link->psr_enabled)
 		return DC_ERROR_UNEXPECTED;
 
+	/* Nothing to compress */
+	if (!pipe_ctx->plane_state)
+		return DC_ERROR_UNEXPECTED;
+
 	/* Only for non-linear tiling */
 	if (pipe_ctx->plane_state->tiling_info.gfx8.array_mode == DC_ARRAY_LINEAR_GENERAL)
 		return DC_ERROR_UNEXPECTED;