char: Disable write callback if throttled chardev is detached

If a throttled chardev is detached from the frontend device, all future
callbacks should be suppressed.  Not doing this results in a segfault.

Bugzilla: 745758
Upstream: Not applicable, since throttling is a RHEL6-only feature.

Signed-off-by: Amit Shah <amit.shah@redhat.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/qemu-char.c b/qemu-char.c
index 1cc36c57b..8c09d0aef 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -224,6 +224,11 @@ void qemu_chr_add_handlers(CharDriverState *s,
         ++s->avail_connections;
     }
     if (!handlers) {
+        if (s->write_blocked) {
+            /* Ensure we disable the callback if we were throttled */
+            s->chr_disable_write_fd_handler(s);
+            /* s->write_blocked is cleared below */
+        }
         handlers = &null_handlers;
     }
     s->chr_can_read = handlers->fd_can_read;