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

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Message-ID: <b25747ca-c8a8-45de-a5e1-f8cf2caa2729@amd.com>
Date: Mon, 27 May 2024 17:01:51 +0200
From: Christian König <christian.koenig@....com>
To: "T.J. Mercier" <tjmercier@...gle.com>, Fedor Pchelkin <pchelkin@...ras.ru>
Cc: 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 v2] dma-buf: handle testing kthreads creation failure

Am 22.05.24 um 20:33 schrieb T.J. Mercier:
> On Wed, May 22, 2024 at 11:14 AM Fedor Pchelkin <pchelkin@...ras.ru> 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@...r.kernel.org
>> Signed-off-by: Fedor Pchelkin <pchelkin@...ras.ru>
> Reviewed-by: T.J. Mercier <tjmercier@...gle.com>

Just FYI: I've picked this one up and pushed it to drm-misc-fixes.

Regards,
Christian.

>> ---
>> 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@ispras.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..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
>>