linux-kernel - [PATCH 3.16 024/357] drm/i915: Fix crash when failing to parse MIPI VBT

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Date:	Fri,  3 Oct 2014 14:26:50 -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, Shobhit Kumar <shobhit.kumar@...el.com>,
	Rafael Barbalho <rafael.barbalho@...el.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>
Subject: [PATCH 3.16 024/357] drm/i915: Fix crash when failing to parse MIPI VBT

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

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

From: Rafael Barbalho <rafael.barbalho@...el.com>

commit ed3b6679936801fa2dab47e7a6ef74e383400ed9 upstream.

This particular nasty presented itself while trying to register the
intelfb device (intel_fbdev.c). During the process of registering the device
the driver will disable the crtc via i9xx_crtc_disable. These will
also disable the panel using the generic mipi panel functions in
dsi_mod_vbt_generic.c. The stale MIPI generic data sequence pointers would
cause a crash within those functions. However, all of this is happening
while console_lock is held from do_register_framebuffer inside fbcon.c. Which
means that you got kernel log and just the device appearing to reboot/hang for
no apparent reason.

The fault started from the FB_EVENT_FB_REGISTERED event using the
fb_notifier_call_chain call in fbcon.c.

This regression has been introduced in

commit d3b542fcfc72d7724585e3fd2c5e75351bc3df47
Author: Shobhit Kumar <shobhit.kumar@...el.com>
Date:   Mon Apr 14 11:00:34 2014 +0530

    drm/i915: Add parsing support for new MIPI blocks in VBT

Cc: Shobhit Kumar <shobhit.kumar@...el.com>
Signed-off-by: Rafael Barbalho <rafael.barbalho@...el.com>
Reviewed-by: Shobhit Kumar <shobhit.kumar@...el.com>
[danvet: Add regression citation.]
Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/i915/intel_bios.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -877,7 +877,7 @@ err:
 
 	/* error during parsing so set all pointers to null
 	 * because of partial parsing */
-	memset(dev_priv->vbt.dsi.sequence, 0, MIPI_SEQ_MAX);
+	memset(dev_priv->vbt.dsi.sequence, 0, sizeof(dev_priv->vbt.dsi.sequence));
 }
 
 static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,


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