qcow2: Check header_length (CVE-2014-0144)

This fixes an unbounded allocation for s->unknown_header_fields.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 25 insertions, 9 deletions

diff --git a/block/qcow2.c b/block/qcow2.c
index 10eccf91e..7809f5cab 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -460,6 +460,18 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
 
     s->qcow_version = header.version;
 
+    /* Initialise cluster size */
+    if (header.cluster_bits < MIN_CLUSTER_BITS ||
+        header.cluster_bits > MAX_CLUSTER_BITS) {
+        error_setg(errp, "Unsupported cluster size: 2^%i", header.cluster_bits);
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    s->cluster_bits = header.cluster_bits;
+    s->cluster_size = 1 << s->cluster_bits;
+    s->cluster_sectors = 1 << (s->cluster_bits - 9);
+
     /* Initialise version 3 header fields */
     if (header.version == 2) {
         header.incompatible_features    = 0;
@@ -473,6 +485,18 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
         be64_to_cpus(&header.autoclear_features);
         be32_to_cpus(&header.refcount_order);
         be32_to_cpus(&header.header_length);
+
+        if (header.header_length < 104) {
+            error_setg(errp, "qcow2 header too short");
+            ret = -EINVAL;
+            goto fail;
+        }
+    }
+
+    if (header.header_length > s->cluster_size) {
+        error_setg(errp, "qcow2 header exceeds cluster size");
+        ret = -EINVAL;
+        goto fail;
     }
 
     if (header.header_length > sizeof(header)) {
@@ -530,12 +554,6 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
     }
     s->refcount_order = header.refcount_order;
 
-    if (header.cluster_bits < MIN_CLUSTER_BITS ||
-        header.cluster_bits > MAX_CLUSTER_BITS) {
-        error_setg(errp, "Unsupported cluster size: 2^%i", header.cluster_bits);
-        ret = -EINVAL;
-        goto fail;
-    }
     if (header.crypt_method > QCOW_CRYPT_AES) {
         error_setg(errp, "Unsupported encryption method: %i",
                    header.crypt_method);
@@ -546,9 +564,7 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
     if (s->crypt_method_header) {
         bs->encrypted = 1;
     }
-    s->cluster_bits = header.cluster_bits;
-    s->cluster_size = 1 << s->cluster_bits;
-    s->cluster_sectors = 1 << (s->cluster_bits - 9);
+
     s->l2_bits = s->cluster_bits - 3; /* L2 is always one cluster */
     s->l2_size = 1 << s->l2_bits;
     bs->total_sectors = header.size / 512;