On 10/30/22 6:37 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.
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 | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
index 8f5848aa144f..ff44c2777b04 100644
--- a/drivers/dma-buf/dma-heap.c
+++ b/drivers/dma-buf/dma-heap.c
@@ -243,11 +243,12 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
return ERR_PTR(-EINVAL);
}
}
- mutex_unlock(&heap_list_lock);
heap = kzalloc(sizeof(*heap), GFP_KERNEL);
- if (!heap)
+ if (!heap) {
+ mutex_unlock(&heap_list_lock);
return ERR_PTR(-ENOMEM);
+ }
heap->name = exp_info->name;
heap->ops = exp_info->ops;
@@ -284,7 +285,6 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
goto err2;
}
/* Add heap to the list */
- mutex_lock(&heap_list_lock);
Good catch!
In general I'd like to hold locks for as short a time as possible and
only bracket the lock associated structure (heap_list). How about we
move the duplicate name check to down here so they are both inside
this one locked section here.
I know this will mean we take a longer unwind error path
if the names are duplicated, but that should be rare and
this will keep all heap_list accesses together.
Thanks,
Andrew
list_add(&heap->list, &heap_list);
mutex_unlock(&heap_list_lock);
@@ -296,6 +296,7 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
xa_erase(&dma_heap_minors, minor);
err0:
kfree(heap);
+ mutex_unlock(&heap_list_lock);
return err_ret;
}
