Calling the validate_vbt before assiging the opregion vbt blob.
Size of the VBT blob cant be more than 6KB when VBT is present
in mailbox 4.

Cc: Jani Nikula <jani.nik...@intel.com>
Signed-off-by: Deepak M <m.dee...@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h       |  3 +++
 drivers/gpu/drm/i915/intel_bios.c     | 43 +++++++++++++++++++----------------
 drivers/gpu/drm/i915/intel_opregion.c | 31 +++++++++++++++++++++++++
 3 files changed, 57 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 135d32a..8cf8375 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3324,6 +3324,9 @@ intel_opregion_notify_adapter(struct drm_device *dev, 
pci_power_t state)
 }
 #endif
 
+const struct vbt_header *validate_vbt(const void *_vbt, size_t size,
+                                               const char *source);
+
 /* intel_acpi.c */
 #ifdef CONFIG_ACPI
 extern void intel_register_dsm_handler(void);
diff --git a/drivers/gpu/drm/i915/intel_bios.c 
b/drivers/gpu/drm/i915/intel_bios.c
index 6756a1c..57a77aa 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -1237,16 +1237,15 @@ static const struct dmi_system_id 
intel_no_opregion_vbt[] = {
        { }
 };
 
-static const struct bdb_header *validate_vbt(const void *base,
+const struct vbt_header *validate_vbt(const void *_vbt,
                                             size_t size,
-                                            const void *_vbt,
                                             const char *source)
 {
-       size_t offset = _vbt - base;
-       const struct vbt_header *vbt = _vbt;
+       const struct vbt_header *vbt = (const struct vbt_header *)_vbt;
        const struct bdb_header *bdb;
+       size_t offset;
 
-       if (offset + sizeof(struct vbt_header) > size) {
+       if (sizeof(struct vbt_header) > size) {
                DRM_DEBUG_DRIVER("VBT header incomplete\n");
                return NULL;
        }
@@ -1256,26 +1255,26 @@ static const struct bdb_header *validate_vbt(const void 
*base,
                return NULL;
        }
 
-       offset += vbt->bdb_offset;
+       offset = vbt->bdb_offset;
        if (offset + sizeof(struct bdb_header) > size) {
                DRM_DEBUG_DRIVER("BDB header incomplete\n");
                return NULL;
        }
 
-       bdb = base + offset;
+       bdb = (const void *)_vbt + offset;
        if (offset + bdb->bdb_size > size) {
                DRM_DEBUG_DRIVER("BDB incomplete\n");
                return NULL;
        }
 
        DRM_DEBUG_KMS("Using VBT from %s: %20s\n",
-                     source, vbt->signature);
-       return bdb;
+                       source, vbt->signature);
+       return vbt;
 }
 
-static const struct bdb_header *find_vbt(void __iomem *bios, size_t size)
+static const struct vbt_header *find_vbt(void __iomem *bios, size_t size)
 {
-       const struct bdb_header *bdb = NULL;
+       const struct vbt_header *vbt = NULL;
        size_t i;
 
        /* Scour memory looking for the VBT signature. */
@@ -1289,12 +1288,12 @@ static const struct bdb_header *find_vbt(void __iomem 
*bios, size_t size)
                         */
                        void *_bios = (void __force *) bios;
 
-                       bdb = validate_vbt(_bios, size, _bios + i, "PCI ROM");
+                       vbt = validate_vbt(_bios + i, size - i, "PCI ROM");
                        break;
                }
        }
 
-       return bdb;
+       return vbt;
 }
 
 /**
@@ -1311,6 +1310,7 @@ intel_parse_bios(struct drm_device *dev)
 {
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct pci_dev *pdev = dev->pdev;
+       const struct vbt_header *vbt = NULL;
        const struct bdb_header *bdb = NULL;
        u8 __iomem *bios = NULL;
 
@@ -1319,23 +1319,26 @@ intel_parse_bios(struct drm_device *dev)
 
        init_vbt_defaults(dev_priv);
 
-       /* XXX Should this validation be moved to intel_opregion.c? */
-       if (!dmi_check_system(intel_no_opregion_vbt) && dev_priv->opregion.vbt)
-               bdb = validate_vbt(dev_priv->opregion.header, OPREGION_SIZE,
-                                  dev_priv->opregion.vbt, "OpRegion");
+       if (!dmi_check_system(intel_no_opregion_vbt) &&
+                                       dev_priv->opregion.vbt) {
+               vbt = (const struct vbt_header *)dev_priv->opregion.vbt;
+               bdb = (const void *)dev_priv->opregion.vbt + vbt->bdb_offset;
+       }
 
-       if (bdb == NULL) {
+       if (vbt == NULL) {
                size_t size;
 
                bios = pci_map_rom(pdev, &size);
                if (!bios)
                        return -1;
 
-               bdb = find_vbt(bios, size);
-               if (!bdb) {
+               vbt = find_vbt(bios, size);
+               if (!vbt) {
                        pci_unmap_rom(pdev, bios);
                        return -1;
                }
+
+               bdb = (const void *)vbt + vbt->bdb_offset;
        }
 
        /* Grab useful general definitions */
diff --git a/drivers/gpu/drm/i915/intel_opregion.c 
b/drivers/gpu/drm/i915/intel_opregion.c
index 43b7c3b..4a78282 100644
--- a/drivers/gpu/drm/i915/intel_opregion.c
+++ b/drivers/gpu/drm/i915/intel_opregion.c
@@ -48,6 +48,27 @@
 #define OPREGION_VBT_OFFSET    0x400
 #define OPREGION_ASLE_EXT_OFFSET       0x1C00
 
+#define MAILBOX_4_SIZE         0x1800
+
+/*
+ *     Opregion Structure:
+ *           +-------------------------------+
+ *            |      Mailbox1 : ACPI          |
+ *            |      Offset   : 0x100         |
+ *            +-------------------------------+
+ *            |      Mailbox2 : SWSCI        |
+ *            |      Offset   : 0x200         |
+ *            +-------------------------------+
+ *            |      Mailbox3 : ASLE         |
+ *            |      Offset   : 0x300         |
+ *            +-------------------------------+
+ *            |      Mailbox4 : VBT          |
+ *            |      Offset   : 0x400         |
+ *            +-------------------------------+
+ *            |      Mailbox5 : ASLE_EXT      |
+ *            |      Offset   : 0x1C00        |
+ *            +-------------------------------+
+*/
 #define OPREGION_SIGNATURE "IntelGraphicsMem"
 #define MBOX_ACPI      (1<<0)
 #define MBOX_SWSCI     (1<<1)
@@ -910,6 +931,7 @@ int intel_opregion_setup(struct drm_device *dev)
        struct intel_opregion *opregion = &dev_priv->opregion;
        u32 asls, mboxes;
        char buf[sizeof(OPREGION_SIGNATURE)];
+       const struct vbt_header *vbt = NULL;
        int err = 0;
        void *base;
 
@@ -940,6 +962,15 @@ int intel_opregion_setup(struct drm_device *dev)
                err = -EINVAL;
                goto err_out;
        }
+
+       vbt = validate_vbt(base + OPREGION_VBT_OFFSET,
+                               MAILBOX_4_SIZE, "OpRegion");
+
+       if (vbt == NULL) {
+               err = -EINVAL;
+               goto err_out;
+       }
+
        opregion->header = base;
        opregion->vbt = base + OPREGION_VBT_OFFSET;
 
-- 
1.9.1

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