Protect iommu_add_dt_device() with dtdevs_lock to prevent concurrent access add.

Signed-off-by: Vikram Garhwal <vikram.garhwal@amd.com>
Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
Reviewed-by: Michal Orzel <michal.orzel@amd.com>
---
 xen/drivers/passthrough/device_tree.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/xen/drivers/passthrough/device_tree.c b/xen/drivers/passthrough/device_tree.c
index 52e370db01..8cc413f867 100644
--- a/xen/drivers/passthrough/device_tree.c
+++ b/xen/drivers/passthrough/device_tree.c
@@ -146,6 +146,8 @@ int iommu_add_dt_device(struct dt_device_node *np)
     if ( dev_iommu_fwspec_get(dev) )
         return 0;
 
+    spin_lock(&dtdevs_lock);
+
     /*
      * According to the Documentation/devicetree/bindings/iommu/iommu.txt
      * from Linux.
@@ -158,7 +160,10 @@ int iommu_add_dt_device(struct dt_device_node *np)
          * these callback implemented.
          */
         if ( !ops->add_device || !ops->dt_xlate )
-            return -EINVAL;
+        {
+            rc = -EINVAL;
+            goto fail;
+        }
 
         if ( !dt_device_is_available(iommu_spec.np) )
             break;
@@ -189,6 +194,8 @@ int iommu_add_dt_device(struct dt_device_node *np)
     if ( rc < 0 )
         iommu_fwspec_free(dev);
 
+fail:
+    spin_unlock(&dtdevs_lock);
     return rc;
 }
 
-- 
2.17.1

Hi,

On 02/06/2023 01:48, Vikram Garhwal wrote:
> Protect iommu_add_dt_device() with dtdevs_lock to prevent concurrent access add.

The commit message is a bit light. What sort of concurrent access add 
are you talking about? Is it of the same node? Different node?

Also, is it a existing issue or something that will become one with a 
follow-up patch in your series?

Cheers,

-- 
Julien Grall

On 02.06.2023 02:48, Vikram Garhwal wrote:
> @@ -189,6 +194,8 @@ int iommu_add_dt_device(struct dt_device_node *np)
>      if ( rc < 0 )
>          iommu_fwspec_free(dev);
>  
> +fail:
> +    spin_unlock(&dtdevs_lock);

Nit: Labels indented by at least on blank please (see ./CODING_STYLE).

Jan