From 30fb2ca603e8b8d0f02630ef18bc0d0637a88ffa Mon Sep 17 00:00:00 2001 From: Amit Shah Date: Wed, 20 Jul 2011 13:30:56 +0530 Subject: [PATCH] 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.c | 17 ++++++++++------- balloon.h | 8 +++++--- hw/virtio-balloon.c | 7 ++----- 3 files changed, 17 insertions(+), 15 deletions(-) diff --git a/balloon.c b/balloon.c index d40be39b3b..8be3812ee2 100644 --- a/balloon.c +++ b/balloon.c @@ -32,30 +32,33 @@ static QEMUBalloonEvent *balloon_event_fn; +static QEMUBalloonStatus *balloon_stat_fn; static void *balloon_opaque; -void qemu_add_balloon_handler(QEMUBalloonEvent *func, void *opaque) +void qemu_add_balloon_handler(QEMUBalloonEvent *event_func, + QEMUBalloonStatus *stat_func, void *opaque) { - balloon_event_fn = func; + balloon_event_fn = event_func; + balloon_stat_fn = stat_func; balloon_opaque = opaque; } -static int qemu_balloon(ram_addr_t target, MonitorCompletion cb, void *opaque) +static int qemu_balloon(ram_addr_t target) { if (!balloon_event_fn) { return 0; } trace_balloon_event(balloon_opaque, target); - balloon_event_fn(balloon_opaque, target, cb, opaque); + balloon_event_fn(balloon_opaque, target); return 1; } static int qemu_balloon_status(MonitorCompletion cb, void *opaque) { - if (!balloon_event_fn) { + if (!balloon_stat_fn) { return 0; } - balloon_event_fn(balloon_opaque, 0, cb, opaque); + balloon_stat_fn(balloon_opaque, cb, opaque); return 1; } @@ -135,7 +138,7 @@ int do_balloon(Monitor *mon, const QDict *params, return -1; } - ret = qemu_balloon(qdict_get_int(params, "value"), cb, opaque); + ret = qemu_balloon(qdict_get_int(params, "value")); if (ret == 0) { qerror_report(QERR_DEVICE_NOT_ACTIVE, "balloon"); return -1; diff --git a/balloon.h b/balloon.h index 06a8a46b50..a6c31d587c 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); diff --git a/hw/virtio-balloon.c b/hw/virtio-balloon.c index 2f371f2f69..40b43b0606 100644 --- a/hw/virtio-balloon.c +++ b/hw/virtio-balloon.c @@ -227,8 +227,7 @@ static void virtio_balloon_stat(void *opaque, MonitorCompletion cb, complete_stats_request(dev); } -static void virtio_balloon_to_target(void *opaque, ram_addr_t target, - MonitorCompletion cb, void *cb_data) +static void virtio_balloon_to_target(void *opaque, ram_addr_t target) { VirtIOBalloon *dev = opaque; @@ -238,8 +237,6 @@ static void virtio_balloon_to_target(void *opaque, ram_addr_t target, if (target) { dev->num_pages = (ram_size - target) >> VIRTIO_BALLOON_PFN_SHIFT; virtio_notify_config(&dev->vdev); - } else { - virtio_balloon_stat(opaque, cb, cb_data); } } @@ -284,7 +281,7 @@ VirtIODevice *virtio_balloon_init(DeviceState *dev) s->svq = virtio_add_queue(&s->vdev, 128, virtio_balloon_receive_stats); reset_stats(s); - qemu_add_balloon_handler(virtio_balloon_to_target, s); + qemu_add_balloon_handler(virtio_balloon_to_target, virtio_balloon_stat, s); register_savevm(dev, "virtio-balloon", -1, 1, virtio_balloon_save, virtio_balloon_load, s);