linux-kernel - Re: [PATCH 2/2] dmaengine: qcom_hidma: fix handoff FIFO memory leak on driver removal

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Message-ID: <3c6513fe-83b3-4117-8df6-6f8c7eb07303@linaro.org>
Date: Thu, 5 Jun 2025 16:04:04 +0300
From: Eugen Hristev <eugen.hristev@...aro.org>
To: Qasim Ijaz <qasdev00@...il.com>, Sinan Kaya <okaya@...nel.org>,
 Vinod Koul <vkoul@...nel.org>, linux-arm-kernel@...ts.infradead.org,
 linux-arm-msm@...r.kernel.org, dmaengine@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: stable@...r.kernel.org
Subject: Re: [PATCH 2/2] dmaengine: qcom_hidma: fix handoff FIFO memory leak
 on driver removal



On 6/2/25 01:42, Qasim Ijaz wrote:
> hidma_ll_init() allocates a handoff FIFO, but the matching 
> hidma_ll_uninit() function (which is invoked in remove()) 
> never releases it, leaking memory.
> 
> To fix this call kfifo_free in hidma_ll_uninit().
> 
> Fixes: d1615ca2e085 ("dmaengine: qcom_hidma: implement lower level hardware interface")
> Cc: stable@...r.kernel.org
> Signed-off-by: Qasim Ijaz <qasdev00@...il.com>
> 
> ---
>  drivers/dma/qcom/hidma_ll.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/dma/qcom/hidma_ll.c b/drivers/dma/qcom/hidma_ll.c
> index fee448499777..0c2bae46746c 100644
> --- a/drivers/dma/qcom/hidma_ll.c
> +++ b/drivers/dma/qcom/hidma_ll.c
> @@ -816,6 +816,7 @@ int hidma_ll_uninit(struct hidma_lldev *lldev)
>  
>  	required_bytes = sizeof(struct hidma_tre) * lldev->nr_tres;
>  	tasklet_kill(&lldev->task);
> +	kfifo_free(&lldev->handoff_fifo);
>  	memset(lldev->trepool, 0, required_bytes);
>  	lldev->trepool = NULL;
>  	atomic_set(&lldev->pending_tre_count, 0);

Is it possible that the handoff_fifo is freed, then we could observe
reset complete interrupts before they are being cleared in
hidma_ll_uninit later on, which would lead to the following call chain

 hidma_ll_inthandler - hidma_ll_int_handler_internal -
hidma_handle_tre_completion - hidma_post_completed -
tasklet_schedule(&lldev->task); - hidma_ll_tre_complete - kfifo_out

?