The following BUG was found when running on a kernel with
CONFIG_DEBUG_MUTEXES=y set:
DEBUG_LOCKS_WARN_ON(lock->magic != lock)
RIP: 0010:mutex_trylock+0x10d/0x120
Call Trace:
<TASK>
? __warn+0x85/0x140
? mutex_trylock+0x10d/0x120
? report_bug+0xfc/0x1e0
? handle_bug+0x3f/0x70
? exc_invalid_op+0x17/0x70
? asm_exc_invalid_op+0x1a/0x20
? mutex_trylock+0x10d/0x120
? mutex_trylock+0x10d/0x120
pds_vfio_reset+0x3a/0x60 [pds_vfio_pci]
pci_reset_function+0x4b/0x70
reset_store+0x5b/0xa0
kernfs_fop_write_iter+0x137/0x1d0
vfs_write+0x2de/0x410
ksys_write+0x5d/0xd0
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x6e/0xd8
As shown, lock->magic != lock. This is because
mutex_init(&pds_vfio->state_mutex) is called in the VFIO open path. So,
if a reset is initiated before the VFIO device is opened the mutex will
have never been initialized. Fix this by calling
mutex_init(&pds_vfio->state_mutex) in the VFIO init path.
Also, don't destroy the mutex on close because the device may
be re-opened, which would cause mutex to be uninitialized. Fix this by
implementing a driver specific vfio_device_ops.release callback that
destroys the mutex before calling vfio_pci_core_release_dev().
Signed-off-by: Brett Creeley <brett.creeley@xxxxxxx>
Reviewed-by: Shannon Nelson <shannon.nelson@xxxxxxx>
---
drivers/vfio/pci/pds/vfio_dev.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/drivers/vfio/pci/pds/vfio_dev.c b/drivers/vfio/pci/pds/vfio_dev.c
index c351f588fa13..306b1c25f016 100644
--- a/drivers/vfio/pci/pds/vfio_dev.c
+++ b/drivers/vfio/pci/pds/vfio_dev.c
@@ -155,6 +155,7 @@ static int pds_vfio_init_device(struct vfio_device *vdev)
pds_vfio->vf_id = vf_id;
+ mutex_init(&pds_vfio->state_mutex);
spin_lock_init(&pds_vfio->reset_lock);
vdev->migration_flags = VFIO_MIGRATION_STOP_COPY | VFIO_MIGRATION_P2P;
@@ -170,6 +171,16 @@ static int pds_vfio_init_device(struct vfio_device *vdev)
return 0;
}
+static void pds_vfio_release_device(struct vfio_device *vdev)
+{
+ struct pds_vfio_pci_device *pds_vfio =
+ container_of(vdev, struct pds_vfio_pci_device,
+ vfio_coredev.vdev);
+
+ mutex_destroy(&pds_vfio->state_mutex);
+ vfio_pci_core_release_dev(vdev);
+}
+
static int pds_vfio_open_device(struct vfio_device *vdev)
{
struct pds_vfio_pci_device *pds_vfio =
@@ -181,7 +192,6 @@ static int pds_vfio_open_device(struct vfio_device *vdev)
if (err)
return err;
- mutex_init(&pds_vfio->state_mutex);
pds_vfio->state = VFIO_DEVICE_STATE_RUNNING;
pds_vfio->deferred_reset_state = VFIO_DEVICE_STATE_RUNNING;
@@ -201,14 +211,13 @@ static void pds_vfio_close_device(struct vfio_device *vdev)
pds_vfio_put_save_file(pds_vfio);
pds_vfio_dirty_disable(pds_vfio, true);
mutex_unlock(&pds_vfio->state_mutex);
- mutex_destroy(&pds_vfio->state_mutex);
vfio_pci_core_close_device(vdev);
}
static const struct vfio_device_ops pds_vfio_ops = {
.name = "pds-vfio",
.init = pds_vfio_init_device,
- .release = vfio_pci_core_release_dev,
+ .release = pds_vfio_release_device,
.open_device = pds_vfio_open_device,
.close_device = pds_vfio_close_device,
.ioctl = vfio_pci_core_ioctl,
--
2.17.1
