netdev - [PATCH] vhost-vdpa: free iommu domain after last use during cleanup

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Date:   Wed, 1 Mar 2023 22:02:01 +0530
From:   Gautam Dawar <gautam.dawar@....com>
To:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        <kvm@...r.kernel.org>, <virtualization@...ts.linux-foundation.org>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <linux-net-drivers@....com>, <harpreet.anand@....com>,
        <tanuj.kamde@....com>, Gautam Dawar <gautam.dawar@....com>
Subject: [PATCH] vhost-vdpa: free iommu domain after last use during cleanup

Currently vhost_vdpa_cleanup() unmaps the DMA mappings by calling
`iommu_unmap(v->domain, map->start, map->size);`
from vhost_vdpa_general_unmap() when the parent vDPA driver doesn't
provide DMA config operations.

However, the IOMMU domain referred to by `v->domain` is freed in
vhost_vdpa_free_domain() before vhost_vdpa_cleanup() in
vhost_vdpa_release() which results in NULL pointer de-reference.
Accordingly, moving the call to vhost_vdpa_free_domain() in
vhost_vdpa_cleanup() would makes sense. This will also help
detaching the dma device in error handling of vhost_vdpa_alloc_domain().

This issue was observed on terminating QEMU with SIGQUIT.

Fixes: 037d4305569a ("vhost-vdpa: call vhost_vdpa_cleanup during the release")
Signed-off-by: Gautam Dawar <gautam.dawar@....com>
---
 drivers/vhost/vdpa.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index ec32f785dfde..b7657984dd8d 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -1134,6 +1134,7 @@ static int vhost_vdpa_alloc_domain(struct vhost_vdpa *v)
 
 err_attach:
 	iommu_domain_free(v->domain);
+	v->domain = NULL;
 	return ret;
 }
 
@@ -1178,6 +1179,7 @@ static void vhost_vdpa_cleanup(struct vhost_vdpa *v)
 			vhost_vdpa_remove_as(v, asid);
 	}
 
+	vhost_vdpa_free_domain(v);
 	vhost_dev_cleanup(&v->vdev);
 	kfree(v->vdev.vqs);
 }
@@ -1250,7 +1252,6 @@ static int vhost_vdpa_release(struct inode *inode, struct file *filep)
 	vhost_vdpa_clean_irq(v);
 	vhost_vdpa_reset(v);
 	vhost_dev_stop(&v->vdev);
-	vhost_vdpa_free_domain(v);
 	vhost_vdpa_config_put(v);
 	vhost_vdpa_cleanup(v);
 	mutex_unlock(&d->mutex);
-- 
2.30.1