New patch to review for coreboot: chromeos: vpd: Avoid reading uninitialized VPDs

[Patrick Georgi]

Patrick Georgi ([e-mail]) just uploaded a new patch set to gerrit, which you can find at https://review.coreboot.org/13467

-gerrit

commit ba8579c1e73a8c307901267e87675b1b1f79f344
Author: Julius Werner 
Date:   Thu Jan 21 11:12:38 2016 -0800

chromeos: vpd: Avoid reading uninitialized VPDs

This patch adds a check to the VPD parsing code to avoid reading the
    whole thing if the first byte ('type' of the first VPD entry) is 0x00
    or 0xff. These values match the TERMINATOR and IMPLICIT_TERMINATOR types
    which should never occur as the first entry, so this usually means that
    the VPD FMAP section has simply never been initialized correctly. This
    early abort avoids wasting time to read the whole section from SPI flash
    (which we'd otherwise have to since we're not going to find a Google VPD
    2.0 header either).

BRANCH=None
    BUG=None
    TEST=Booted Oak, confirmed that VPD read times dropped from 100ms to
    1.5ms.

Change-Id: I9fc473e06440aef4e1023238fb9e53d45097ee9d
    Signed-off-by: Patrick Georgi 
    Original-Commit-Id: 20a726237e03941ad626a6146700170a45ee7720
    Original-Change-Id: I09bfec3c24d24214fa4e9180878b58d00454f399
    Original-Signed-off-by: Julius Werner 
    Original-Reviewed-on: https://chromium-review.googlesource.com/322897
    Original-Reviewed-by: Hung-Te Lin 
---
 src/vendorcode/google/chromeos/cros_vpd.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/vendorcode/google/chromeos/cros_vpd.c b/src/vendorcode/google/chromeos/cros_vpd.c
index e826d36..d0e2cc1 100644
--- a/src/vendorcode/google/chromeos/cros_vpd.c
+++ b/src/vendorcode/google/chromeos/cros_vpd.c
@@ -65,11 +65,21 @@ static int32_t get_vpd_size(const char *fmap_name, int32_t *base)
    }

/* Try if we can find a google_vpd_info, otherwise read whole VPD. */
-	if (rdev_readat(&vpd, &info, *base, sizeof(info)) == sizeof(info) &&
-	    memcmp(info.header.magic, VPD_INFO_MAGIC, sizeof(info.header.magic))
+	if (rdev_readat(&vpd, &info, *base, sizeof(info)) != sizeof(info)) {
+		printk(BIOS_ERR, "ERROR: Failed to read %s header.\n",
+		       fmap_name);
+		return 0;
+	}
+
+	if (memcmp(info.header.magic, VPD_INFO_MAGIC, sizeof(info.header.magic))
        == 0 && size >= info.size + sizeof(info)) {
    	*base += sizeof(info);
    	size = info.size;
+	} else if (info.header.tlv.type == VPD_TYPE_TERMINATOR ||
+		   info.header.tlv.type == VPD_TYPE_IMPLICIT_TERMINATOR) {
+		printk(BIOS_WARNING, "WARNING: %s is uninitialized or empty.\n",
+		       fmap_name);
+		size = 0;
    } else {
    	size -= GOOGLE_VPD_2_0_OFFSET;
    }