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@outlook.com

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; }