From 691f5a3510ba83d25806f8eefa3b0d642d498dd5 Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Sun, 19 Mar 2017 20:38:40 -0600 Subject: [PATCH] drm/i915/kvmgt: Hold struct kvm reference BugLink: http://bugs.launchpad.net/bugs/1681875 commit 93a15b58cfb8a24e666ffca432f19fe65c1cd7d1 upstream. The kvmgt code keeps a pointer to the struct kvm associated with the device, but doesn't actually hold a reference to it. If we do unclean shutdown testing (ie. killing the user process), then we can see the kvm association to the device unset, which causes kvmgt to trigger a device release via a work queue. Naturally we cannot guarantee that the cached struct kvm pointer is still valid at this point without holding a reference. The observed failure in this case is a stuck cpu trying to acquire the spinlock from the invalid reference, but other failure modes are clearly possible. Hold a reference to avoid this. Signed-off-by: Alex Williamson Cc: Jike Song Cc: Paolo Bonzini Cc: Zhenyu Wang Cc: Zhi Wang Reviewed-by: Jike Song Signed-off-by: Zhenyu Wang Signed-off-by: Greg Kroah-Hartman Signed-off-by: Tim Gardner --- drivers/gpu/drm/i915/gvt/kvmgt.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c index 3f656e3a6e5a..325cb9b55989 100644 --- a/drivers/gpu/drm/i915/gvt/kvmgt.c +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c @@ -1334,6 +1334,7 @@ static int kvmgt_guest_init(struct mdev_device *mdev) vgpu->handle = (unsigned long)info; info->vgpu = vgpu; info->kvm = kvm; + kvm_get_kvm(info->kvm); kvmgt_protect_table_init(info); gvt_cache_init(vgpu); @@ -1353,6 +1354,7 @@ static bool kvmgt_guest_exit(struct kvmgt_guest_info *info) } kvm_page_track_unregister_notifier(info->kvm, &info->track_node); + kvm_put_kvm(info->kvm); kvmgt_protect_table_destroy(info); gvt_cache_destroy(info->vgpu); vfree(info); -- 2.39.5