From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rodrigo Vivi Subject: [PATCH 06/14] drm/i915: Validate VBT header before trusting it Date: Fri, 18 Apr 2014 18:04:22 -0300 Message-ID: <1397855070-4480-7-git-send-email-rodrigo.vivi@gmail.com> References: <1397855070-4480-1-git-send-email-rodrigo.vivi@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pd0-f178.google.com (mail-pd0-f178.google.com [209.85.192.178]) by gabe.freedesktop.org (Postfix) with ESMTP id 3331E6ECF1 for ; Fri, 18 Apr 2014 14:04:42 -0700 (PDT) Received: by mail-pd0-f178.google.com with SMTP id x10so1766578pdj.23 for ; Fri, 18 Apr 2014 14:04:42 -0700 (PDT) In-Reply-To: <1397855070-4480-1-git-send-email-rodrigo.vivi@gmail.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: intel-gfx@lists.freedesktop.org List-Id: intel-gfx@lists.freedesktop.org From: Chris Wilson Be we read and chase pointers from the VBT, it is prudent to make sure that those accesses are wholly contained within the MMIO region, or else we may cause a kernel panic during boot. Signed-off-by: Chris Wilson Signed-off-by: Rodrigo Vivi --- drivers/gpu/drm/i915/intel_bios.c | 68 ++++++++++++++++++++++++++++----------- 1 file changed, 50 insertions(+), 18 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c index fba9efd..fc9e806 100644 --- a/drivers/gpu/drm/i915/intel_bios.c +++ b/drivers/gpu/drm/i915/intel_bios.c @@ -1099,6 +1099,46 @@ static const struct dmi_system_id intel_no_opregion_vbt[] = { { } }; +static struct bdb_header *validate_vbt(char *base, size_t size, + struct vbt_header *vbt, + const char *source) +{ + size_t offset; + struct bdb_header *bdb; + + if (vbt == NULL) { + DRM_DEBUG_DRIVER("VBT signature missing\n"); + return NULL; + } + + offset = (char *)vbt - base; + if (offset + sizeof(struct vbt_header) > size) { + DRM_DEBUG_DRIVER("VBT header incomplete\n"); + return NULL; + } + + if (memcmp(vbt->signature, "$VBT", 4)) { + DRM_DEBUG_DRIVER("VBT invalid signature\n"); + return NULL; + } + + offset += vbt->bdb_offset; + if (offset + sizeof(struct bdb_header) > size) { + DRM_DEBUG_DRIVER("BDB header incomplete\n"); + return NULL; + } + + bdb = (struct bdb_header *)(base + offset); + if (offset + bdb->bdb_size > size) { + DRM_DEBUG_DRIVER("BDB incomplete\n"); + return NULL; + } + + DRM_DEBUG_KMS("Using VBT from %s: %20s\n", + source, vbt->signature); + return bdb; +} + /** * intel_parse_bios - find VBT and initialize settings from the BIOS * @dev: DRM device @@ -1122,20 +1162,13 @@ intel_parse_bios(struct drm_device *dev) init_vbt_defaults(dev_priv); /* XXX Should this validation be moved to intel_opregion.c? */ - if (!dmi_check_system(intel_no_opregion_vbt) && dev_priv->opregion.vbt) { - struct vbt_header *vbt = dev_priv->opregion.vbt; - if (memcmp(vbt->signature, "$VBT", 4) == 0) { - DRM_DEBUG_KMS("Using VBT from OpRegion: %20s\n", - vbt->signature); - bdb = (struct bdb_header *)((char *)vbt + vbt->bdb_offset); - } else - dev_priv->opregion.vbt = NULL; - } + if (!dmi_check_system(intel_no_opregion_vbt) && dev_priv->opregion.vbt) + bdb = validate_vbt((char *)dev_priv->opregion.header, OPREGION_SIZE, + (struct vbt_header *)dev_priv->opregion.vbt, + "OpRegion"); if (bdb == NULL) { - struct vbt_header *vbt = NULL; - size_t size; - int i; + size_t i, size; bios = pci_map_rom(pdev, &size); if (!bios) @@ -1143,19 +1176,18 @@ intel_parse_bios(struct drm_device *dev) /* Scour memory looking for the VBT signature */ for (i = 0; i + 4 < size; i++) { - if (!memcmp(bios + i, "$VBT", 4)) { - vbt = (struct vbt_header *)(bios + i); + if (memcmp(bios + i, "$VBT", 4) == 0) { + bdb = validate_vbt(bios, size, + (struct vbt_header *)(bios + i), + "PCI ROM"); break; } } - if (!vbt) { - DRM_DEBUG_DRIVER("VBT signature missing\n"); + if (!bdb) { pci_unmap_rom(pdev, bios); return -1; } - - bdb = (struct bdb_header *)(bios + i + vbt->bdb_offset); } /* Grab useful general definitions */ -- 1.8.3.1