linux-kernel - Re: [PATCH 5.10 14/86] dmaengine: mediatek:Fix PM usage reference leak of mtk_uart_apdma_alloc_chan

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Date:   Wed, 27 Apr 2022 22:32:48 +0200
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Zhang Qilong <zhangqilong3@...wei.com>,
        Vinod Koul <vkoul@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 5.10 14/86] dmaengine: mediatek:Fix PM usage reference
 leak of mtk_uart_apdma_alloc_chan_resources

Hi!

> > pm_runtime_get_sync will increment pm usage counter even it failed.
> > Forgetting to putting operation will result in reference leak here.
> > We fix it:
> > 1) Replacing it with pm_runtime_resume_and_get to keep usage counter
> >    balanced.
> 
> Suspect.
> 
> > 2) Add putting operation before returning error.
> 
> Yes but you also put in success case, which is likely
> wrong. mtk_uart_apdma_free_chan_resources() does second put.

This is possible fix for the second problem:

Signed-off-by: Pavel Machek <pavel@...x.de>

diff --git a/drivers/dma/mediatek/mtk-uart-apdma.c b/drivers/dma/mediatek/mtk-uart-apdma.c
index a1517ef1f4a0..8ec046a7e714 100644
--- a/drivers/dma/mediatek/mtk-uart-apdma.c
+++ b/drivers/dma/mediatek/mtk-uart-apdma.c
@@ -300,7 +300,8 @@ static int mtk_uart_apdma_alloc_chan_resources(struct dma_chan *chan)
 
 	if (mtkd->support_33bits)
 		mtk_uart_apdma_write(c, VFF_4G_SUPPORT, VFF_4G_SUPPORT_CLR_B);
-
+	return 0;
+	
 err_pm:
 	pm_runtime_put_noidle(mtkd->ddev.dev);
 	return ret;

Best regards,
								Pavel

-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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