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

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Date: Wed, 22 May 2024 10:40:39 -0700
From: "T.J. Mercier" <tjmercier@...gle.com>
To: Fedor Pchelkin <pchelkin@...ras.ru>
Cc: Christian König <christian.koenig@....com>, 
	Sumit Semwal <sumit.semwal@...aro.org>, Chris Wilson <chris@...is-wilson.co.uk>, 
	Daniel Vetter <daniel.vetter@...ll.ch>, linux-media@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org, 
	linux-kernel@...r.kernel.org, Alexey Khoroshilov <khoroshilov@...ras.ru>, 
	lvc-project@...uxtesting.org, stable@...r.kernel.org
Subject: Re: [PATCH] dma-buf: handle testing kthreads creation failure

On Wed, May 22, 2024 at 5:24 AM Fedor Pchelkin <pchelkin@...ras.ru> wrote:
>
> kthread creation may possibly fail inside race_signal_callback(). In
> such case stop the already started threads and return with error code.
>
> Found by Linux Verification Center (linuxtesting.org).
>
> Fixes: 2989f6451084 ("dma-buf: Add selftests for dma-fence")
> Cc: stable@...r.kernel.org
> Signed-off-by: Fedor Pchelkin <pchelkin@...ras.ru>
> ---
>  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..ab1ec4631578 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(t[i].task);

This looks like it needs to be kthread_stop_put since get_task_struct
was called for previous successful kthread_run calls.

> +                               return ret;
> +                       }
>                         get_task_struct(t[i].task);
>                 }
>
> --
> 2.39.2
>