Created attachment 1025310 [details]
afl9.img

Description of problem:

The attached disk image demonstrates a bug in the VMDK driver
where it returns a bogus negative value from bdrv_getlength.

Apparently negative values should be -errno, but in this case
it returns a very large negative value.

Demonstration:

  $ qemu-img info afl9.img
  qemu-img: Can't get size of device 'image': Unknown error -512

Using gdb at the point where the error message is displayed
we can see that size has a bogus value:

  $ gdb --args ./qemu-img info /mnt/scratch/afl9.img 
  (gdb) list block/qapi.c:209
  204	    Error *err = NULL;
  205	    ImageInfo *info;
  206	
  207	    size = bdrv_getlength(bs);
  208	    if (size < 0) {
  209	        error_setg_errno(errp, -size, "Can't get size of device '%s'",
  210	                         bdrv_get_device_name(bs));
  211	        return;
  212	    }
  213	
  (gdb) break block/qapi.c:209
  Breakpoint 1 at 0x51708: file block/qapi.c, line 209.
  (gdb) run
  # gdb breaks at the breakpoint set above
  (gdb) print size
  $1 = -8564164787712
  (gdb) print/x size
  $2 = 0xfffff83600000200

Apparently when -size is passed to error_setg_errno, it is truncated
to 0x200 (512), thus causing the bogus error message to be printed:

  qemu-img: Can't get size of device 'image': Unknown error -512

Version-Release number of selected component (if applicable):

qemu from git

How reproducible:

100%

Steps to Reproduce:
1. See above.