From 30fb2ca603e8b8d0f02630ef18bc0d0637a88ffa Mon Sep 17 00:00:00 2001 From: Amit Shah Date: Wed, 20 Jul 2011 13:30:56 +0530 Subject: balloon: Separate out stat and balloon handling Passing on '0' as ballooning target to indicate retrieval of stats is bad API. It also makes 'balloon 0' in the monitor cause a segfault. Have two different functions handle the different functionality instead. Detailed explanation from Markus's review: 1. do_info_balloon() is an info_async() method. It receives a callback with argument, to be called exactly once (callback frees the argument). It passes the callback via qemu_balloon_status() and indirectly through qemu_balloon_event to virtio_balloon_to_target(). virtio_balloon_to_target() executes its balloon stats half. It stores the callback in the device state. If it can't send a stats request, it resets stats and calls the callback right away. Else, it sends a stats request. The device model runs the callback when it receives the answer. Works. 2. do_balloon() is a cmd_async() method. It receives a callback with argument, to be called when the command completes. do_balloon() calls it right before it succeeds. Odd, but should work. Nevertheless, it passes the callback on via qemu_ballon() and indirectly through qemu_balloon_event to virtio_balloon_to_target(). a. If the argument is non-zero, virtio_balloon_to_target() executes its balloon half, which doesn't use the callback in any way. Odd, but works. b. If the argument is zero, virtio_balloon_to_target() executes its balloon stats half, just like in 1. It either calls the callback right away, or arranges for it to be called later. Thus, the callback runs twice: use after free and double free. Test case: start with -S -device virtio-balloon, execute "balloon 0" in human monitor. Runs the callback first from virtio_balloon_to_target(), then again from do_balloon(). Reported-by: Mike Cao Signed-off-by: Amit Shah Reviewed-by: Markus Armbruster --- balloon.h | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'balloon.h') diff --git a/balloon.h b/balloon.h index 06a8a46b5..a6c31d587 100644 --- a/balloon.h +++ b/balloon.h @@ -16,10 +16,12 @@ #include "monitor.h" -typedef void (QEMUBalloonEvent)(void *opaque, ram_addr_t target, - MonitorCompletion cb, void *cb_data); +typedef void (QEMUBalloonEvent)(void *opaque, ram_addr_t target); +typedef void (QEMUBalloonStatus)(void *opaque, MonitorCompletion cb, + void *cb_data); -void qemu_add_balloon_handler(QEMUBalloonEvent *func, void *opaque); +void qemu_add_balloon_handler(QEMUBalloonEvent *event_func, + QEMUBalloonStatus *stat_func, void *opaque); void monitor_print_balloon(Monitor *mon, const QObject *data); int do_info_balloon(Monitor *mon, MonitorCompletion cb, void *opaque); -- cgit v1.2.3