[Qemu-devel] [PATCH v2 for-2.0 1/2] vdi: add bounds checks for blocks_in_image and disk_size header fields (CVE-2014-0144)

[Jeff Cody <jcody@redhat.com>]

The maximum blocks_in_image is 0xffffffff / 4, which also limits the
maximum disk_size for a VDI image to 1024TB.  Note that this is the maximum
size that QEMU will currently support with this driver, not necessarily the
maximum size allowed by the image format.

This also fixes an incorrect error message, a bug introduced by commit
5b7aa9b56d1bfc79916262f380c3fc7961becb50 (Reported by Stefan Weil)

Signed-off-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/vdi.c | 37 +++++++++++++++++++++++++++++++++----
 1 file changed, 33 insertions(+), 4 deletions(-)

diff --git a/block/vdi.c b/block/vdi.c
index ac9a025..820cd37 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -120,6 +120,11 @@ typedef unsigned char uuid_t[16];
 
 #define VDI_IS_ALLOCATED(X) ((X) < VDI_DISCARDED)
 
+/* max blocks in image is (0xffffffff / 4) */
+#define VDI_BLOCKS_IN_IMAGE_MAX  0x3fffffff
+#define VDI_DISK_SIZE_MAX        ((uint64_t)VDI_BLOCKS_IN_IMAGE_MAX * \
+                                  (uint64_t)DEFAULT_CLUSTER_SIZE)
+
 #if !defined(CONFIG_UUID)
 static inline void uuid_generate(uuid_t out)
 {
@@ -385,6 +390,14 @@ static int vdi_open(BlockDriverState *bs, QDict *options, int flags,
     vdi_header_print(&header);
 #endif
 
+    if (header.disk_size > VDI_DISK_SIZE_MAX) {
+        error_setg(errp, "Unsupported VDI image size (size is 0x%" PRIx64
+                          ", max supported is 0x%" PRIx64 ")",
+                          header.disk_size, VDI_DISK_SIZE_MAX);
+        ret = -ENOTSUP;
+        goto fail;
+    }
+
     if (header.disk_size % SECTOR_SIZE != 0) {
         /* 'VBoxManage convertfromraw' can create images with odd disk sizes.
            We accept them but round the disk size to the next multiple of
@@ -420,9 +433,9 @@ static int vdi_open(BlockDriverState *bs, QDict *options, int flags,
                    header.sector_size, SECTOR_SIZE);
         ret = -ENOTSUP;
         goto fail;
-    } else if (header.block_size != 1 * MiB) {
-        error_setg(errp, "unsupported VDI image (sector size %u is not %u)",
-                   header.block_size, 1 * MiB);
+    } else if (header.block_size != DEFAULT_CLUSTER_SIZE) {
+        error_setg(errp, "unsupported VDI image (block size %u is not %u)",
+                   header.block_size, DEFAULT_CLUSTER_SIZE);
         ret = -ENOTSUP;
         goto fail;
     } else if (header.disk_size >
@@ -441,6 +454,12 @@ static int vdi_open(BlockDriverState *bs, QDict *options, int flags,
         error_setg(errp, "unsupported VDI image (non-NULL parent UUID)");
         ret = -ENOTSUP;
         goto fail;
+    } else if (header.blocks_in_image > VDI_BLOCKS_IN_IMAGE_MAX) {
+        error_setg(errp, "unsupported VDI image "
+                         "(too many blocks %u, max is %u)",
+                          header.blocks_in_image, VDI_BLOCKS_IN_IMAGE_MAX);
+        ret = -ENOTSUP;
+        goto fail;
     }
 
     bs->total_sectors = header.disk_size / SECTOR_SIZE;
@@ -689,11 +708,20 @@ static int vdi_create(const char *filename, QEMUOptionParameter *options,
         options++;
     }
 
+    if (bytes > VDI_DISK_SIZE_MAX) {
+        result = -ENOTSUP;
+        error_setg(errp, "Unsupported VDI image size (size is 0x%" PRIx64
+                          ", max supported is 0x%" PRIx64 ")",
+                          bytes, VDI_DISK_SIZE_MAX);
+        goto exit;
+    }
+
     fd = qemu_open(filename,
                    O_WRONLY | O_CREAT | O_TRUNC | O_BINARY | O_LARGEFILE,
                    0644);
     if (fd < 0) {
-        return -errno;
+        result = -errno;
+        goto exit;
     }
 
     /* We need enough blocks to store the given disk size,
@@ -754,6 +782,7 @@ static int vdi_create(const char *filename, QEMUOptionParameter *options,
         result = -errno;
     }
 
+exit:
     return result;
 }
 
-- 
1.8.3.1