block: Guard against NULL bs->drv
We currently do not guard everywhere against a NULL bs->drv where we
should be doing so. Most of the places fixed here just do not care
about that case at all.
Some care implicitly, e.g. through a prior function call to
bdrv_getlength() which would always fail for an ejected BDS. Add an
assert there to make it more obvious.
Other places seem to care, but do so insufficiently: Freeing clusters in
a qcow2 image is an error-free operation, but it may leave the image in
an unusable state anyway. Giving qcow2_free_clusters() an error code is
not really viable, it is much easier to note that bs->drv may be NULL
even after a successful driver call. This concerns bdrv_co_flush(), and
the way the check is added to bdrv_co_pdiscard() (in every iteration
instead of only once).
Finally, some places employ at least an assert(bs->drv); somewhere, that
may be reasonable (such as in the reopen code), but in
bdrv_has_zero_init(), it is definitely not. Returning 0 there in case
of an ejected BDS saves us much headache instead.
Reported-by: R. Nageswara Sastry <nasastry@in.ibm.com>
Buglink: https://bugs.launchpad.net/qemu/+bug/1728660
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20171110203111.7666-4-mreitz@redhat.com
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
diff --git a/block.c b/block.c
index 70c6d7c..996778c 100644
--- a/block.c
+++ b/block.c
@@ -720,6 +720,10 @@
{
BlockDriver *drv = bs->drv;
+ if (!drv) {
+ return -ENOMEDIUM;
+ }
+
/* Do not attempt drv->bdrv_getlength() on scsi-generic devices */
if (bdrv_is_sg(bs))
return 0;
@@ -3431,6 +3435,10 @@
BlockDriver *drv = bs->drv;
int ret;
+ if (!drv) {
+ return -ENOMEDIUM;
+ }
+
/* Backing file format doesn't make sense without a backing file */
if (backing_fmt && !backing_file) {
return -EINVAL;
@@ -3916,7 +3924,9 @@
int bdrv_has_zero_init(BlockDriverState *bs)
{
- assert(bs->drv);
+ if (!bs->drv) {
+ return 0;
+ }
/* If BS is a copy on write image, it is initialized to
the contents of the base image, which may not be zeroes. */
@@ -4256,6 +4266,10 @@
BdrvChild *child, *parent;
int ret;
+ if (!bs->drv) {
+ return -ENOMEDIUM;
+ }
+
if (!setting_flag && bs->drv->bdrv_inactivate) {
ret = bs->drv->bdrv_inactivate(bs);
if (ret < 0) {
@@ -4790,6 +4804,9 @@
int bdrv_amend_options(BlockDriverState *bs, QemuOpts *opts,
BlockDriverAmendStatusCB *status_cb, void *cb_opaque)
{
+ if (!bs->drv) {
+ return -ENOMEDIUM;
+ }
if (!bs->drv->bdrv_amend_options) {
return -ENOTSUP;
}
