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

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Message-Id: <20240522181308.841686-1-pchelkin@ispras.ru>
Date: Wed, 22 May 2024 21:13:08 +0300
From: Fedor Pchelkin <pchelkin@...ras.ru>
To: Christian König <christian.koenig@....com>,
	Sumit Semwal <sumit.semwal@...aro.org>
Cc: Fedor Pchelkin <pchelkin@...ras.ru>,
	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,
	"T.J. Mercier" <tjmercier@...gle.com>,
	stable@...r.kernel.org
Subject: [PATCH v2] dma-buf: handle testing kthreads creation failure

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>
---
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