[Qemu-devel] [PATCH 085/156] vhdx: Bounds checking for block_size and logical_sector_size (CVE-2014-0148)

[Michael Roth]

From: Jeff Cody <address@hidden>

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 <address@hidden>
Signed-off-by: Jeff Cody <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
Reviewed-by: Max Reitz <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
(cherry picked from commit 1d7678dec4761acdc43439da6ceda41a703ba1a6)
Signed-off-by: Michael Roth <address@hidden>
---
 block/vhdx.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/block/vhdx.c b/block/vhdx.c
index 7d1af96..8a70ae8 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -785,12 +785,20 @@ 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 /
-- 
1.9.1