aboutsummaryrefslogtreecommitdiff
path: root/block.c
diff options
context:
space:
mode:
authorRyan Harper <ryanh@us.ibm.com>2011-03-29 20:51:47 -0500
committerKevin Wolf <kwolf@redhat.com>2011-04-07 13:51:47 +0200
commitd22b2f41c470067758b3636a01b452dfeda7069f (patch)
tree327f9815ca8157d2324f4c2a732e9683bc400b2b /block.c
parentf6ec953ca329d4509e5a1a1ff051365fccdbb6b7 (diff)
Do not delete BlockDriverState when deleting the drive
When removing a drive from the host-side via drive_del we currently have the following path: drive_del qemu_aio_flush() bdrv_close() // zaps bs->drv, which makes any subsequent I/O get // dropped. Works as designed drive_uninit() bdrv_delete() // frees the bs. Since the device is still connected to // bs, any subsequent I/O is a use-after-free. The value of bs->drv becomes unpredictable on free. As long as it remains null, I/O still gets dropped, however it could become non-null at any point after the free resulting SEGVs or other QEMU state corruption. To resolve this issue as simply as possible, we can chose to not actually delete the BlockDriverState pointer. Since bdrv_close() handles setting the drv pointer to NULL, we just need to remove the BlockDriverState from the QLIST that is used to enumerate the block devices. This is currently handled within bdrv_delete, so move this into its own function, bdrv_make_anon(). The result is that we can now invoke drive_del, this closes the file descriptors and sets BlockDriverState->drv to NULL which prevents futher IO to the device, and since we do not free BlockDriverState, we don't have to worry about the copy retained in the block devices. We also don't attempt to remove the qdev property since we are no longer deleting the BlockDriverState on drives with associated drives. This also allows for removing Drives with no devices associated either. Reported-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Ryan Harper <ryanh@us.ibm.com> Acked-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block.c')
-rw-r--r--block.c14
1 files changed, 11 insertions, 3 deletions
diff --git a/block.c b/block.c
index c8e2f97614..c93ec6d418 100644
--- a/block.c
+++ b/block.c
@@ -697,14 +697,22 @@ void bdrv_close_all(void)
}
}
+/* make a BlockDriverState anonymous by removing from bdrv_state list.
+ Also, NULL terminate the device_name to prevent double remove */
+void bdrv_make_anon(BlockDriverState *bs)
+{
+ if (bs->device_name[0] != '\0') {
+ QTAILQ_REMOVE(&bdrv_states, bs, list);
+ }
+ bs->device_name[0] = '\0';
+}
+
void bdrv_delete(BlockDriverState *bs)
{
assert(!bs->peer);
/* remove from list, if necessary */
- if (bs->device_name[0] != '\0') {
- QTAILQ_REMOVE(&bdrv_states, bs, list);
- }
+ bdrv_make_anon(bs);
bdrv_close(bs);
if (bs->file != NULL) {