linux-kernel - Re: [PATCH] dma-buf: fix reference count leak in dma_buf_poll_add

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Message-ID: <aNKQZqWwWu_8WesG@stanley.mountain>
Date: Tue, 23 Sep 2025 15:19:50 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Christian König <christian.koenig@....com>
Cc: Sumit Semwal <sumit.semwal@...aro.org>,
	Simona Vetter <simona.vetter@...ll.ch>, linux-media@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] dma-buf: fix reference count leak in
 dma_buf_poll_add_cb()

On Tue, Sep 23, 2025 at 02:00:28PM +0200, Christian König wrote:
> On 23.09.25 13:14, Dan Carpenter wrote:
> > Call dma_fence_put(fence) if dma_fence_add_callback() fails.
> 
> Well that change is obviously incorrect.
>
> When dma_fence_add_callback() fails we already call dma_fence_put() and drop the reference.
> 
> When the dma_fence_add_callback() call succeeds the callback will drop the reference.
> 
> The problem here is that the return code of dma_fence_add_callback() is an integer error code instead of a bool and basically has the reverse meaning than what people usually expect.
> 

Ah, yes.  You're exactly correct of course.  Sorry about that.

regards,
dan carpenter