On Mon, Jan 22, 2018 at 09:01:49AM -0600, Mark Kanda wrote:
Add a BlockDriverState NULL check to virtio_blk_handle_request()
to prevent a segfault if the drive is forcibly removed using HMP
'drive_del' (without performing a hotplug 'device_del' first).
Signed-off-by: Mark Kanda <address@hidden>
Reviewed-by: Karl Heubaum <address@hidden>
Reviewed-by: Ameya More <address@hidden>
---
hw/block/virtio-blk.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index b1532e4..76ddbbf 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -507,6 +507,13 @@ static int virtio_blk_handle_request(VirtIOBlockReq *req,
MultiReqBuffer *mrb)
return -1;
}
+ /* If the drive was forcibly removed (e.g. HMP 'drive_del'), the block
+ * driver state may be NULL and there is nothing left to do. */
+ if (!blk_bs(req->dev->blk)) {
Adding Markus Armbruster to check my understanding of drive_del:
1. If id is a node name (e.g. created via blockdev-add) then attempting
to remove the root node produces the "Node %s is in use" error. In
that case this patch isn't needed.
2. If id is a BlockBackend (e.g. created via -drive) then removing the
root node is allowed. The BlockBackend stays in place but blk->root
becomes NULL, hence this patch is needed.
Markus: What are the valid use cases for #2? If blk->bs becomes NULL I
would think a lot more code beyond virtio-blk can segfault.