vhdx: Bounds checking for block_size and logical_sector_size (CVE-2014-0148)

Other variables (e.g. sectors_per_block) are calculated using these
variables, and if not range-checked illegal values could be obtained
causing infinite loops and other potential issues when calculating
BAT entries.

The 1.00 VHDX spec requires BlockSize to be min 1MB, max 256MB.
LogicalSectorSize is required to be either 512 or 4096 bytes.

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

diff --git a/block/vhdx.c b/block/vhdx.c
index e9704b1fdc1c119ea52280b3080bd6c729c63b9e..36fc06c2cf0740ea253873b8d0ec0ef548930344 100644 (file)
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -627,12 +627,20 @@ static int vhdx_parse_metadata(BlockDriverState *bs, BDRVVHDXState *s)
     le32_to_cpus(&s->logical_sector_size);
     le32_to_cpus(&s->physical_sector_size);
 
-    if (s->logical_sector_size == 0 || s->params.block_size == 0) {
+    if (s->params.block_size < VHDX_BLOCK_SIZE_MIN ||
+        s->params.block_size > VHDX_BLOCK_SIZE_MAX) {
         ret = -EINVAL;
         goto exit;
     }
 
-    /* both block_size and sector_size are guaranteed powers of 2 */
+    /* only 2 supported sector sizes */
+    if (s->logical_sector_size != 512 && s->logical_sector_size != 4096) {
+        ret = -EINVAL;
+        goto exit;
+    }
+
+    /* Both block_size and sector_size are guaranteed powers of 2, below.
+       Due to range checks above, s->sectors_per_block can never be < 256 */
     s->sectors_per_block = s->params.block_size / s->logical_sector_size;
     s->chunk_ratio = (VHDX_MAX_SECTORS_PER_BLOCK) *
                      (uint64_t)s->logical_sector_size /

diff --git a/block/vhdx.h b/block/vhdx.h
index fb687ed2d6b7c4aa21376234c679b826d291eb46..77844e34246b575b18885173abb1ca4aff77db8f 100644 (file)
--- a/block/vhdx.h
+++ b/block/vhdx.h
@@ -18,6 +18,11 @@
 #ifndef BLOCK_VHDX_H
 #define BLOCK_VHDX_H
 
+#define KiB              (1 * 1024)
+#define MiB            (KiB * 1024)
+#define GiB            (MiB * 1024)
+#define TiB ((uint64_t) GiB * 1024)
+
 /* Structures and fields present in the VHDX file */
 
 /* The header section has the following blocks,
@@ -262,6 +267,8 @@ typedef struct QEMU_PACKED VHDXMetadataTableEntry {
                                                    If set indicates a fixed
                                                    size VHDX file */
 #define VHDX_PARAMS_HAS_PARENT           0x02    /* has parent / backing file */
+#define VHDX_BLOCK_SIZE_MIN             (1   * MiB)
+#define VHDX_BLOCK_SIZE_MAX             (256 * MiB)
 typedef struct QEMU_PACKED VHDXFileParameters {
     uint32_t    block_size;             /* size of each payload block, always
                                            power of 2, <= 256MB and >= 1MB. */