[PULL 06/17] dmg: refuse to open files with no chunks

From: Stefan Hajnoczi <[email protected]>

The dmg block driver expects the disk image file to contain at least one
chunk. Refuse to open such files. This ensures that dmg block driver
state always has non-NULL s->sectors[] and related fields.

Note that the previous commit fixed the only known way to trigger a
crash. This patch is just for defense - let's avoid opening the file and
having NULL pointers in dmg block driver state.

Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/4021
Reported-by: Tristan Madani <[email protected]>
Signed-off-by: Stefan Hajnoczi <[email protected]>
Message-ID: <[email protected]>
Reviewed-by: Kevin Wolf <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>
---
 block/dmg.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/block/dmg.c b/block/dmg.c
index e325127d144..6f8120e0338 100644
--- a/block/dmg.c
+++ b/block/dmg.c
@@ -559,6 +559,12 @@ static int dmg_open(BlockDriverState *bs, QDict *options, int flags,
         goto fail;
     }
 
+    /* There must be at least one chunk */
+    if (s->n_chunks == 0) {
+        ret = -EINVAL;
+        goto fail;
+    }
+
     /* initialize zlib engine */
     s->compressed_chunk = qemu_try_blockalign(bs->file->bs,
                                               ds.max_compressed_size + 1);
-- 
2.55.0