diff mbox series

[v2,vfio,2/3] pds/vfio: Fix mutex lock->magic != lock warning

Message ID 20231011230115.35719-3-brett.creeley@amd.com (mailing list archive)
State New, archived
Headers show
Series pds/vfio: Fixes for locking bugs | expand

Commit Message

Brett Creeley Oct. 11, 2023, 11:01 p.m. UTC 
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@amd.com>
Reviewed-by: Shannon Nelson <shannon.nelson@amd.com>
---
 drivers/vfio/pci/pds/vfio_dev.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

Comments

Shameerali Kolothum Thodi Oct. 12, 2023, 9 a.m. UTC | #1 
> -----Original Message-----
> From: Brett Creeley [mailto:brett.creeley@amd.com]
> Sent: 12 October 2023 00:01
> To: jgg@ziepe.ca; yishaih@nvidia.com; Shameerali Kolothum Thodi
> <shameerali.kolothum.thodi@huawei.com>; kevin.tian@intel.com;
> alex.williamson@redhat.com; dan.carpenter@linaro.org
> Cc: kvm@vger.kernel.org; linux-kernel@vger.kernel.org;
> brett.creeley@amd.com; shannon.nelson@amd.com
> Subject: [PATCH v2 vfio 2/3] pds/vfio: Fix mutex lock->magic != lock warning
> 
> 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@amd.com>
> Reviewed-by: Shannon Nelson <shannon.nelson@amd.com>

Reviewed-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>

Looks like mutex destruction logic needs to be added to HiSilicon driver as well.
From a quick look mlx5 also doesn't destroy the state_mutex.

Thanks,
Shameer
 
> ---
>  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
Jason Gunthorpe Oct. 12, 2023, 1:50 p.m. UTC | #2 
On Thu, Oct 12, 2023 at 09:00:09AM +0000, Shameerali Kolothum Thodi wrote:

> > 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@amd.com>
> > Reviewed-by: Shannon Nelson <shannon.nelson@amd.com>
> 
> Reviewed-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> 
> Looks like mutex destruction logic needs to be added to HiSilicon driver as well.
> From a quick look mlx5 also doesn't destroy the state_mutex.

FWIW, mutex_destroy is a debugging feature, it is nice if you can do it, but
not a bug if it is missing..

Jason
diff mbox series

Patch

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,