| From 1f177df6a47fb1e2961067a50e005efad52595cc Mon Sep 17 00:00:00 2001 |
| From: Ladi Prosek <lprosek@redhat.com> |
| Date: Wed, 5 Oct 2016 17:22:26 +0200 |
| Subject: [PATCH 4/8] balloon: fix segfault and harden the stats queue |
| |
| RH-Author: Ladi Prosek <lprosek@redhat.com> |
| Message-id: <1475666548-9186-5-git-send-email-lprosek@redhat.com> |
| Patchwork-id: 72483 |
| O-Subject: [RHEL-7.4 qemu-kvm v2 PATCH 4/6] balloon: fix segfault and harden the stats queue |
| Bugzilla: 1377968 |
| RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com> |
| RH-Acked-by: Michael S. Tsirkin <mst@redhat.com> |
| RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com> |
| |
| The segfault here is triggered by the driver notifying the stats queue |
| twice after adding a buffer to it. This effectively resets stats_vq_elem |
| back to NULL and QEMU crashes on the next stats timer tick in |
| balloon_stats_poll_cb. |
| |
| This is a regression introduced in 51b19ebe4320f3dc, although admittedly |
| the device assumed too much about the stats queue protocol even before |
| that commit. This commit adds a few more checks and ensures that the one |
| stats buffer gets deallocated on device reset. |
| |
| Cc: qemu-stable@nongnu.org |
| Signed-off-by: Ladi Prosek <lprosek@redhat.com> |
| Reviewed-by: Michael S. Tsirkin <mst@redhat.com> |
| Signed-off-by: Michael S. Tsirkin <mst@redhat.com> |
| (cherry picked from commit 4eae2a657d1ff5ada56eb9b4966eae0eff333b0b) |
| Signed-off-by: Ladi Prosek <lprosek@redhat.com> |
| Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com> |
| |
| Conflicts: |
| * 1.5.3 does not return pointers from virtqueue_pop so only the |
| "harden the stats queue" part of the upstream patch description |
| applies |
| * a new field stats_vq_elem_pending is introduced to keep track |
| of the state of stats_vq_elem in lieu of its nullness upstream |
| * virtio_balloon_device_reset only resets stats_vq_elem_pending |
| because there is nothing to free |
| |
| hw/virtio/virtio-balloon.c | 27 +++++++++++++++++++++++---- |
| include/hw/virtio/virtio-balloon.h | 1 + |
| 2 files changed, 24 insertions(+), 4 deletions(-) |
| |
| diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c |
| index 016dc60..17b3029 100644 |
| |
| |
| @@ -95,13 +95,14 @@ static void balloon_stats_poll_cb(void *opaque) |
| VirtIOBalloon *s = opaque; |
| VirtIODevice *vdev = VIRTIO_DEVICE(s); |
| |
| - if (!balloon_stats_supported(s)) { |
| + if (!s->stats_vq_elem_pending || !balloon_stats_supported(s)) { |
| /* re-schedule */ |
| balloon_stats_change_timer(s, s->stats_poll_interval); |
| return; |
| } |
| |
| virtqueue_push(s->svq, &s->stats_vq_elem, s->stats_vq_offset); |
| + s->stats_vq_elem_pending = false; |
| virtio_notify(vdev, s->svq); |
| } |
| |
| @@ -220,14 +221,22 @@ static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq) |
| static void virtio_balloon_receive_stats(VirtIODevice *vdev, VirtQueue *vq) |
| { |
| VirtIOBalloon *s = VIRTIO_BALLOON(vdev); |
| - VirtQueueElement *elem = &s->stats_vq_elem; |
| + VirtQueueElement elem; |
| VirtIOBalloonStat stat; |
| size_t offset = 0; |
| qemu_timeval tv; |
| |
| - if (!virtqueue_pop(vq, elem)) { |
| + if (!virtqueue_pop(vq, &elem)) { |
| goto out; |
| } |
| + if (s->stats_vq_elem_pending) { |
| + /* This should never happen if the driver follows the spec. */ |
| + virtqueue_push(vq, &s->stats_vq_elem, 0); |
| + virtio_notify(vdev, vq); |
| + } |
| + |
| + s->stats_vq_elem = elem; |
| + s->stats_vq_elem_pending = true; |
| |
| /* Initialize the stats to get rid of any stale values. This is only |
| * needed to handle the case where a guest supports fewer stats than it |
| @@ -235,7 +244,7 @@ static void virtio_balloon_receive_stats(VirtIODevice *vdev, VirtQueue *vq) |
| */ |
| reset_stats(s); |
| |
| - while (iov_to_buf(elem->out_sg, elem->out_num, offset, &stat, sizeof(stat)) |
| + while (iov_to_buf(elem.out_sg, elem.out_num, offset, &stat, sizeof(stat)) |
| == sizeof(stat)) { |
| uint16_t tag = tswap16(stat.tag); |
| uint64_t val = tswap64(stat.val); |
| @@ -384,6 +393,15 @@ static void virtio_balloon_device_exit(VirtIODevice *vdev) |
| virtio_cleanup(vdev); |
| } |
| |
| +static void virtio_balloon_device_reset(VirtIODevice *vdev) |
| +{ |
| + VirtIOBalloon *s = VIRTIO_BALLOON(vdev); |
| + |
| + if (s->stats_vq_elem_pending) { |
| + s->stats_vq_elem_pending = false; |
| + } |
| +} |
| + |
| static Property virtio_balloon_properties[] = { |
| DEFINE_PROP_END_OF_LIST(), |
| }; |
| @@ -396,6 +414,7 @@ static void virtio_balloon_class_init(ObjectClass *klass, void *data) |
| set_bit(DEVICE_CATEGORY_MISC, dc->categories); |
| vdc->init = virtio_balloon_device_init; |
| vdc->exit = virtio_balloon_device_exit; |
| + vdc->reset = virtio_balloon_device_reset; |
| vdc->get_config = virtio_balloon_get_config; |
| vdc->set_config = virtio_balloon_set_config; |
| vdc->get_features = virtio_balloon_get_features; |
| diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h |
| index f863bfe..a84736b 100644 |
| |
| |
| @@ -63,6 +63,7 @@ typedef struct VirtIOBalloon { |
| uint32_t actual; |
| uint64_t stats[VIRTIO_BALLOON_S_NR]; |
| VirtQueueElement stats_vq_elem; |
| + bool stats_vq_elem_pending; |
| size_t stats_vq_offset; |
| QEMUTimer *stats_timer; |
| int64_t stats_last_update; |
| -- |
| 1.8.3.1 |
| |