Re: [PATCH v2] dma-buf: handle testing kthreads creation failure

[T.J. Mercier]

On Wed, May 22, 2024 at 11:14 AM Fedor Pchelkin <pchelkin@xxxxxxxxx> wrote:
>
> kthread creation may possibly fail inside race_signal_callback(). In
> such a case stop the already started threads, put the already taken
> references to them and return with error code.
>
> Found by Linux Verification Center (linuxtesting.org).
>
> Fixes: 2989f6451084 ("dma-buf: Add selftests for dma-fence")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Fedor Pchelkin <pchelkin@xxxxxxxxx>
Reviewed-by: T.J. Mercier <tjmercier@xxxxxxxxxx>
> ---
> v2: use kthread_stop_put() to actually put the last reference as
>     T.J. Mercier noticed;
>     link to v1: https://lore.kernel.org/lkml/20240522122326.696928-1-pchelkin@xxxxxxxxx/
>
>  drivers/dma-buf/st-dma-fence.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/dma-buf/st-dma-fence.c b/drivers/dma-buf/st-dma-fence.c
> index b7c6f7ea9e0c..6a1bfcd0cc21 100644
> --- a/drivers/dma-buf/st-dma-fence.c
> +++ b/drivers/dma-buf/st-dma-fence.c
> @@ -540,6 +540,12 @@ static int race_signal_callback(void *arg)
>                         t[i].before = pass;
>                         t[i].task = kthread_run(thread_signal_callback, &t[i],
>                                                 "dma-fence:%d", i);
> +                       if (IS_ERR(t[i].task)) {
> +                               ret = PTR_ERR(t[i].task);
> +                               while (--i >= 0)
> +                                       kthread_stop_put(t[i].task);
> +                               return ret;
> +                       }
>                         get_task_struct(t[i].task);
>                 }
>
> --
> 2.39.2
>