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SubjectRe: [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@TYCP286MB2323.JPNP286.PROD.OUTLOOK.COM/
>
> 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@outlook.com>
> ---
> 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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