Re: [Qemu-devel] [PATCH v2 04/37] hw/usb-storage: Check whether BB is inserted

[Kevin Wolf]

Am 04.03.2015 um 15:07 hat Max Reitz geschrieben:
> On 2015-03-04 at 09:02, Kevin Wolf wrote:
> >Am 09.02.2015 um 18:11 hat Max Reitz geschrieben:
> >>Only call bdrv_key_required() on the BlockDriverState if the
> >>BlockBackend has an inserted medium.
> >>
> >>Signed-off-by: Max Reitz <address@hidden>
> >>Reviewed-by: Eric Blake <address@hidden>
> >>---
> >>  hw/usb/dev-storage.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >>diff --git a/hw/usb/dev-storage.c b/hw/usb/dev-storage.c
> >>index 4539733..3123baf 100644
> >>--- a/hw/usb/dev-storage.c
> >>+++ b/hw/usb/dev-storage.c
> >>@@ -638,7 +638,7 @@ static void usb_msd_realize_storage(USBDevice *dev, 
> >>Error **errp)
> >>      usb_msd_handle_reset(dev);
> >>      s->scsi_dev = scsi_dev;
> >>-    if (bdrv_key_required(blk_bs(blk))) {
> >>+    if (blk_is_inserted(blk) && bdrv_key_required(blk_bs(blk))) {
> >>          if (cur_mon) {
> >>              monitor_read_bdrv_key_start(cur_mon, blk_bs(blk),
> >>                                          usb_msd_password_cb, s);
> >Why would bdrv_key_required() ever return true when no medium is
> >inserted? Sounds like a bug to me, like not resetting state correctly on
> >bdrv_close() of an encrypted image.
> 
> The point is that blk_bs(blk) might be NULL.

This is not what blk_is_inserted() is checking. It happens to protect
you against segfaults because it's robust against using NULL, but with
an existing BDS, checking whether there is a medium inserted (in the
physical device for passthrough drivers) doesn't make sense.

It looks like what you want is blk_bs(blk) != NULL.

Kevin