iotests: Add test for image header overlap

Add a test for an image with an unallocated image header; instead of an
assertion, this should result in the image being marked corrupt.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/060

@@ -164,6 +164,15 @@ wait_break 0
 write 64k 64k
 resume 0" | $QEMU_IO | _filter_qemu_io
 
+echo
+echo "=== Testing unallocated image header ==="
+echo
+_make_test_img 64M
+# Create L1/L2
+$QEMU_IO -c "$OPEN_RW" -c "write 0 64k" | _filter_qemu_io
+poke_file "$TEST_IMG" "$rb_offset" "\x00\x00"
+$QEMU_IO -c "$OPEN_RW" -c "write 64k 64k" | _filter_qemu_io
+
 # success, all done
 echo "*** done"
 rm -f $seq.full

tests/qemu-iotests/060.out

@@ -93,4 +93,12 @@ blkdebug: Suspended request '0'
 write failed: Input/output error
 blkdebug: Resuming request '0'
 aio_write failed: No medium found
+
+=== Testing unallocated image header ===
+
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 
+wrote 65536/65536 bytes at offset 0
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qcow2: Preventing invalid write on metadata (overlaps with qcow2_header); image marked as corrupt.
+write failed: Input/output error
 *** done