Kevin Wolf <kw...@redhat.com> writes: > scsi-disks decides whether it has a read-only device by looking at > whether the BlockBackend specified as drive=... is read-only. In the > case of an anonymous BlockBackend (with a node name specified in > drive=...), this is the read-only flag of the attached node. In the case > of an empty anonymous BlockBackend, it's always read-write because > nothing prevented it from being read-write. > > This is a problem because scsi-cd would take write permissions on the > anonymous BlockBackend of an empty drive created without a drive=... > option. Using blockdev-insert-medium with a read-only node fails then > with the error message "Block node is read-only". > > Fix scsi_realize() so that scsi-cd devices always take read-only > permissions on their BlockBackend instead. > > Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1733920 > Signed-off-by: Kevin Wolf <kw...@redhat.com> > --- > hw/scsi/scsi-disk.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c > index 8e95e3e38d..af3e622dc5 100644 > --- a/hw/scsi/scsi-disk.c > +++ b/hw/scsi/scsi-disk.c > @@ -2318,6 +2318,7 @@ static void > scsi_disk_unit_attention_reported(SCSIDevice *dev) > static void scsi_realize(SCSIDevice *dev, Error **errp) > { > SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, dev); > + bool read_only; > > if (!s->qdev.conf.blk) { > error_setg(errp, "drive property not set"); > @@ -2351,8 +2352,13 @@ static void scsi_realize(SCSIDevice *dev, Error **errp) > return; > } > } > - if (!blkconf_apply_backend_options(&dev->conf, > - blk_is_read_only(s->qdev.conf.blk), > + > + read_only = blk_is_read_only(s->qdev.conf.blk); > + if (dev->type == TYPE_ROM) { > + read_only = true; > + } > + > + if (!blkconf_apply_backend_options(&dev->conf, read_only, > dev->type == TYPE_DISK, errp)) { > return; > }
For what it's worth, we have code similar to the one after this patch in * ide_dev_initfn() * xen_block_realize() (I guess) We have code similar to the one before this patch in * floppy_drive_realize() I figure we avoid the problem by recomputing read-only on media change, in fd_change_cb(). Funny: looks like a medium's read-only-ness lingers after unload until the next medium is loaded. * nvme_realize() * virtio_blk_device_realize() * scsi_generic_realize() * usb_msd_storage_realize() Are these all okay? Should they work more like floppy? If not, what makes floppy special?
