On Wed, Nov 2, 2022 at 8:59 AM Dawei Li <set_pte_at@xxxxxxxxxxx> 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. > > 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 > Reviewed-by: T.J. Mercier <tjmercier@xxxxxxxxxx> Thanks!
