[PATCH] block/vhdx: Add alignment checks for region tables

[Thomas Huth <thuth@redhat.com>]

According to the VHDX specification:

 "The FileOffset and Length fields specify the 64-bit byte offset and 32-bit
  byte length of the object within the file. The values must be a multiple of
  1 MB, and FileOffset must be at least 1 MB."

Thus let's add a sanity check to avoid that bad things could happen later.

Buglink: https://gitlab.com/qemu-project/qemu/-/work_items/3762
Reported-by: Daniel Wade <danjwade95@gmail.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 v2: Use QEMU_IS_ALIGNED() as suggested by Eric

 block/vhdx.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/block/vhdx.c b/block/vhdx.c
index 8013a90a1a4..21270988b5a 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -566,6 +566,16 @@ vhdx_open_region_tables(BlockDriverState *bs, BDRVVHDXState *s)
 
         vhdx_region_entry_le_import(&rt_entry);
 
+        /*
+         * According to the VHDX spec, offset and length must be multiple
+         * of 1 MiB and length must be at least 1 MiB.
+         */
+        if (!QEMU_IS_ALIGNED(rt_entry.file_offset, MiB) ||
+            !QEMU_IS_ALIGNED(rt_entry.length, MiB) || !rt_entry.length) {
+            ret = -EINVAL;
+            goto fail;
+        }
+
         /* check for region overlap between these entries, and any
          * other memory regions in the file */
         ret = vhdx_region_check(s, rt_entry.file_offset, rt_entry.length);
-- 
2.56.0