Re: [PATCH v3] dma-buf: fix racing conflict of dma_heap_add()

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On 11/2/22 10:58 AM, Dawei Li wrote:
Racing conflict could be:
task A                 task B
list_for_each_entry
strcmp(h->name))
                        list_for_each_entry
                        strcmp(h->name)
kzalloc                kzalloc
......                 .....
device_create          device_create
list_add
                        list_add

The root cause is that task B has no idea about the fact someone
else(A) has inserted heap with same name when it calls list_add,
so a potential collision occurs.

v1: https://lore.kernel.org/all/TYCP286MB2323950197F60FC3473123B7CA349@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/

v1->v2: Narrow down locking scope, check the existence of heap before
insertion, as suggested by Andrew Davis.

v2->v3: Remove double checking.

The above version info should be in a cover letter or below
the --- line so it doesn't end up in the commit message in tree.


Fixes: c02a81fba74f ("dma-buf: Add dma-buf heaps framework")

base-commit: 447fb14bf07905b880c9ed1ea92c53d6dd0649d7


Same as above, plus this is an odd base, maybe just use "v6.1-rc2".

Signed-off-by: Dawei Li <set_pte_at@xxxxxxxxxxx>
---
  drivers/dma-buf/dma-heap.c | 29 +++++++++++++++--------------
  1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
index 8f5848aa144f..7a25e98259ea 100644
--- a/drivers/dma-buf/dma-heap.c
+++ b/drivers/dma-buf/dma-heap.c
@@ -233,18 +233,6 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
  		return ERR_PTR(-EINVAL);
  	}
- /* check the name is unique */
-	mutex_lock(&heap_list_lock);
-	list_for_each_entry(h, &heap_list, list) {
-		if (!strcmp(h->name, exp_info->name)) {
-			mutex_unlock(&heap_list_lock);
-			pr_err("dma_heap: Already registered heap named %s\n",
-			       exp_info->name);
-			return ERR_PTR(-EINVAL);
-		}
-	}
-	mutex_unlock(&heap_list_lock);
-
  	heap = kzalloc(sizeof(*heap), GFP_KERNEL);
  	if (!heap)
  		return ERR_PTR(-ENOMEM);
@@ -283,13 +271,26 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
  		err_ret = ERR_CAST(dev_ret);
  		goto err2;
  	}
-	/* Add heap to the list */
+
  	mutex_lock(&heap_list_lock);
+	/* check the name is unique */
+	list_for_each_entry(h, &heap_list, list) {
+		if (!strcmp(h->name, exp_info->name)) {
+			mutex_unlock(&heap_list_lock);
+			pr_err("dma_heap: Already registered heap named %s\n",
+			       exp_info->name);
+			err_ret = ERR_PTR(-EINVAL);
+			goto err3;
+		}
+	}
+
+	/* Add heap to the list */
  	list_add(&heap->list, &heap_list);
  	mutex_unlock(&heap_list_lock);
return heap;
-

Would like to keep this new line after the return statement.

Andrew

+err3:
+	device_destroy(dma_heap_class, heap->heap_devt);
  err2:
  	cdev_del(&heap->heap_cdev);
  err1:



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