char: remove watch callback on chardev detach from frontend
If a frontend device releases the chardev (via unplug), the chr handlers
are set to NULL via qdev's exit callbacks invoking
qemu_chr_add_handlers(). If the chardev had a pending operation, a
callback will be invoked, which will try to access data in the
just-released frontend, causing a segfault.
Ensure the callbacks are disabled when frontends release chardevs.
This was seen when a virtio-serial port was unplugged when heavy
guest->host IO was in progress (causing a callback to be registered).
In the window in which the throttling was active, unplugging ports
caused a qemu segfault.
https://bugzilla.redhat.com/show_bug.cgi?id=985205
CC: <qemu-stable@nongnu.org>
Reported-by: Sibiao Luo <sluo@redhat.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
diff --git a/qemu-char.c b/qemu-char.c
index 0a0833f..6f111ab 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -193,6 +193,8 @@
va_end(ap);
}
+static void remove_fd_in_watch(CharDriverState *chr);
+
void qemu_chr_add_handlers(CharDriverState *s,
IOCanReadHandler *fd_can_read,
IOReadHandler *fd_read,
@@ -203,6 +205,7 @@
if (!opaque && !fd_can_read && !fd_read && !fd_event) {
fe_open = 0;
+ remove_fd_in_watch(s);
} else {
fe_open = 1;
}
