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.
Fixes: c02a81fba74f ("dma-buf: Add dma-buf heaps framework")
base-commit: 447fb14bf07905b880c9ed1ea92c53d6dd0649d7
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;
-
+err3:
+ device_destroy(dma_heap_class, heap->heap_devt);
err2:
cdev_del(&heap->heap_cdev);
err1:
--
2.25.1
