linux-kernel - [PATCH 1/1] vhost: Protect the virtqueue from being cleared whilst still in use

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Date:   Mon, 14 Mar 2022 08:43:02 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     lee.jones@...aro.org, mst@...hat.com, jasowang@...hat.com
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        stable@...r.kernel.org
Subject: [PATCH 1/1] vhost: Protect the virtqueue from being cleared whilst still in use

vhost_vsock_handle_tx_kick() already holds the mutex during its call
to vhost_get_vq_desc().  All we have to do here is take the same lock
during virtqueue clean-up and we mitigate the reported issues.

Also WARN() as a precautionary measure.  The purpose of this is to
capture possible future race conditions which may pop up over time.

Cc: <stable@...r.kernel.org>
Signed-off-by: Lee Jones <lee.jones@...aro.org>
---
 drivers/vhost/vhost.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 59edb5a1ffe28..bbaff6a5e21b8 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -693,6 +693,7 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
 	int i;
 
 	for (i = 0; i < dev->nvqs; ++i) {
+		mutex_lock(&dev->vqs[i]->mutex);
 		if (dev->vqs[i]->error_ctx)
 			eventfd_ctx_put(dev->vqs[i]->error_ctx);
 		if (dev->vqs[i]->kick)
@@ -700,6 +701,7 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
 		if (dev->vqs[i]->call_ctx.ctx)
 			eventfd_ctx_put(dev->vqs[i]->call_ctx.ctx);
 		vhost_vq_reset(dev, dev->vqs[i]);
+		mutex_unlock(&dev->vqs[i]->mutex);
 	}
 	vhost_dev_free_iovecs(dev);
 	if (dev->log_ctx)
-- 
2.35.1.723.g4982287a31-goog