Re: [PATCH][RFC] dmaengine: idxd: Fix possible Use-After-Free in irq_process_work_list

[Dave Jiang <dave.jiang@intel.com>]

On 5/26/24 11:19 PM, Li RongQing wrote:
> I think when the description is freed, it maybe used again because of
s/description/descriptor/

> race, then it's next maybe pointer a value that should not be freed
> 
> To prevent this, list_for_each_entry_safe should be used.
> 
> Signed-off-by: Li RongQing <lirongqing@baidu.com>
> ---
>  drivers/dma/idxd/irq.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/idxd/irq.c b/drivers/dma/idxd/irq.c
> index 8dc029c..0c7fed7 100644
> --- a/drivers/dma/idxd/irq.c
> +++ b/drivers/dma/idxd/irq.c
> @@ -611,7 +611,7 @@ static void irq_process_work_list(struct idxd_irq_entry *irq_entry)
>  
>  	spin_unlock(&irq_entry->list_lock);
>  
> -	list_for_each_entry(desc, &flist, list) {
> +	list_for_each_entry_safe(desc, n, &flist, list) {
>  		/*
>  		 * Check against the original status as ABORT is software defined
>  		 * and 0xff, which DSA_COMP_STATUS_MASK can mask out.

I see what you are pointing at. I think you will also need a
list_del(&desc->list);
immediately after the comments.

Because if the descriptor is freed and given out to a different thread while the code is still walking the list, the iterator may hit a bad pointer due to the freed descriptor pointing to something else.

Also, please include a Fixes tag for the fix. Thanks!