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* [PATCH] dma-buf: WARN on dmabuf release with pending attachments
@ 2021-07-23 12:31 Charan Teja Reddy
  2021-07-23 12:34 ` Christian König
  0 siblings, 1 reply; 3+ messages in thread
From: Charan Teja Reddy @ 2021-07-23 12:31 UTC (permalink / raw)
  To: sumit.semwal, christian.koenig
  Cc: linux-media, dri-devel, linaro-mm-sig, linux-kernel, vinmenon,
	Charan Teja Reddy

It is expected from the clients to follow the below steps on an imported
dmabuf fd:
a) dmabuf = dma_buf_get(fd) // Get the dmabuf from fd
b) dma_buf_attach(dmabuf); // Clients attach to the dmabuf
   o Here the kernel does some slab allocations, say for
dma_buf_attachment and may be some other slab allocation in the
c) Client may need to do dma_buf_map_attachment().
d) Accordingly dma_buf_unmap_attachment() should be called.
e) dma_buf_detach () // Clients detach to the dmabuf.
   o Here the slab allocations made in b) are freed.
f) dma_buf_put(dmabuf) // Can free the dmabuf if it is the last

Now say an erroneous client failed at step c) above thus it directly
called dma_buf_put(), step f) above. Considering that it may be the last
reference to the dmabuf, buffer will be freed with pending attachments
left to the dmabuf which can show up as the 'memory leak'. This should
at least be reported as the WARN().

Signed-off-by: Charan Teja Reddy <>
 drivers/dma-buf/dma-buf.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 511fe0d..733c8b1 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -79,6 +79,7 @@ static void dma_buf_release(struct dentry *dentry)
 	if (dmabuf->resv == (struct dma_resv *)&dmabuf[1])
+	WARN_ON(!list_empty(&dmabuf->attachments));
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of the Code Aurora Forum, hosted by The Linux Foundation

^ permalink raw reply related	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2021-07-23 15:01 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-07-23 12:31 [PATCH] dma-buf: WARN on dmabuf release with pending attachments Charan Teja Reddy
2021-07-23 12:34 ` Christian König
2021-07-23 15:01   ` Daniel Vetter

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