diff options
| author | Alex Williamson <alex.williamson@redhat.com> | 2017-06-19 09:10:32 -0600 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-07-27 15:08:03 -0700 |
| commit | e91a55790ddfbda7f9f72963e561d9c738f14a52 (patch) | |
| tree | bd8e958ed90b2a9d407ae7ca77887c82eba82fe7 | |
| parent | fee760fc6c79998efc48bd06afeec31824dfb2d4 (diff) | |
vfio: Fix group release deadlock
commit 811642d8d8a82c0cce8dc2debfdaf23c5a144839 upstream.
If vfio_iommu_group_notifier() acquires a group reference and that
reference becomes the last reference to the group, then vfio_group_put
introduces a deadlock code path where we're trying to unregister from
the iommu notifier chain from within a callout of that chain. Use a
work_struct to release this reference asynchronously.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/vfio/vfio.c | 37 |
1 files changed, 36 insertions, 1 deletions
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c index d1d70e0b011b..8e8b73b05e54 100644 --- a/drivers/vfio/vfio.c +++ b/drivers/vfio/vfio.c @@ -419,6 +419,34 @@ static void vfio_group_put(struct vfio_group *group) kref_put_mutex(&group->kref, vfio_group_release, &vfio.group_lock); } +struct vfio_group_put_work { + struct work_struct work; + struct vfio_group *group; +}; + +static void vfio_group_put_bg(struct work_struct *work) +{ + struct vfio_group_put_work *do_work; + + do_work = container_of(work, struct vfio_group_put_work, work); + + vfio_group_put(do_work->group); + kfree(do_work); +} + +static void vfio_group_schedule_put(struct vfio_group *group) +{ + struct vfio_group_put_work *do_work; + + do_work = kmalloc(sizeof(*do_work), GFP_KERNEL); + if (WARN_ON(!do_work)) + return; + + INIT_WORK(&do_work->work, vfio_group_put_bg); + do_work->group = group; + schedule_work(&do_work->work); +} + /* Assume group_lock or group reference is held */ static void vfio_group_get(struct vfio_group *group) { @@ -743,7 +771,14 @@ static int vfio_iommu_group_notifier(struct notifier_block *nb, break; } - vfio_group_put(group); + /* + * If we're the last reference to the group, the group will be + * released, which includes unregistering the iommu group notifier. + * We hold a read-lock on that notifier list, unregistering needs + * a write-lock... deadlock. Release our reference asynchronously + * to avoid that situation. + */ + vfio_group_schedule_put(group); return NOTIFY_OK; } |