[PATCH 3.16.y-ckt 003/142] drm/i915/dsi: defend gpio table against out of bounds access

[Luis Henriques]

3.16.7-ckt26 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Jani Nikula <jani.nikula@xxxxxxxxx>

commit 4db3a2448ec8902310acb78de39b6227a9a56ac8 upstream.

Do not blindly trust the VBT data used for indexing.

Reviewed-by: Ville SyrjÃlà <ville.syrjala@xxxxxxxxxxxxxxx>
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
Link: http://patchwork.freedesktop.org/patch/msgid/cc32d40c2b47f2d2151811855ac2c3dabab1d57d.1454582914.git.jani.nikula@xxxxxxxxx
(cherry picked from commit 5d2d0a12d3d08bf50434f0b5947bb73bac04b941)
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/i915/intel_dsi_panel_vbt.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c b/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
index 21a0d348cedc..9db5dc8f4521 100644
--- a/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
+++ b/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
@@ -173,6 +173,11 @@ static u8 *mipi_exec_gpio(struct intel_dsi *intel_dsi, u8 *data)
 	/* pull up/down */
 	action = *data++;
 
+	if (gpio >= ARRAY_SIZE(gtable)) {
+		DRM_DEBUG_KMS("unknown gpio %u\n", gpio);
+		goto out;
+	}
+
 	function = gtable[gpio].function_reg;
 	pad = gtable[gpio].pad_reg;
 
@@ -190,6 +195,7 @@ static u8 *mipi_exec_gpio(struct intel_dsi *intel_dsi, u8 *data)
 	vlv_gpio_nc_write(dev_priv, pad, val);
 	mutex_unlock(&dev_priv->dpio_lock);
 
+out:
 	return data;
 }