| Message ID | 1496437930-12654-2-git-send-email-kwolf@redhat.com |
|---|---|
| State | New |
| Headers | show |
Am 02.06.2017 um 23:12 hat Kevin Wolf geschrieben: > The final bdrv_set_backing_hd() could be working on already freed nodes > because the commit job drops its references (through BlockBackends) to > both overlay_bs and top already a bit earlier. > > One way to trigger the bug is hot unplugging a disk for which > blockdev_mark_auto_del() cancels the block job. > > Fix this by taking BDS-level references while we're still using the > nodes. > > Signed-off-by: Kevin Wolf <kwolf@redhat.com> Cc: qemu-stable@nongnu.org
diff --git a/block/commit.c b/block/commit.c index a3028b2..af6fa68 100644 --- a/block/commit.c +++ b/block/commit.c @@ -89,6 +89,10 @@ static void commit_complete(BlockJob *job, void *opaque) int ret = data->ret; bool remove_commit_top_bs = false; + /* Make sure overlay_bs and top stay around until bdrv_set_backing_hd() */ + bdrv_ref(top); + bdrv_ref(overlay_bs); + /* Remove base node parent that still uses BLK_PERM_WRITE/RESIZE before * the normal backing chain can be restored. */ blk_unref(s->base); @@ -124,6 +128,9 @@ static void commit_complete(BlockJob *job, void *opaque) if (remove_commit_top_bs) { bdrv_set_backing_hd(overlay_bs, top, &error_abort); } + + bdrv_unref(overlay_bs); + bdrv_unref(top); } static void coroutine_fn commit_run(void *opaque)
The final bdrv_set_backing_hd() could be working on already freed nodes because the commit job drops its references (through BlockBackends) to both overlay_bs and top already a bit earlier. One way to trigger the bug is hot unplugging a disk for which blockdev_mark_auto_del() cancels the block job. Fix this by taking BDS-level references while we're still using the nodes. Signed-off-by: Kevin Wolf <kwolf@redhat.com> --- block/commit.c | 7 +++++++ 1 file changed, 7 insertions(+)