linux-kernel - Re: [PATCH 4.19 46/72] net: xilinx: fix possible object reference leak

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Message-ID: <20190503100816.GD5834@amd>
Date:   Fri, 3 May 2019 12:08:16 +0200
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Wen Yang <wen.yang99@....com.cn>,
        Anirudha Sarangi <anirudh@...inx.com>,
        John Linn <John.Linn@...inx.com>,
        "David S. Miller" <davem@...emloft.net>,
        Michal Simek <michal.simek@...inx.com>, netdev@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        "Sasha Levin (Microsoft)" <sashal@...nel.org>
Subject: Re: [PATCH 4.19 46/72] net: xilinx: fix possible object reference
 leak

On Thu 2019-05-02 17:21:08, Greg Kroah-Hartman wrote:
> [ Upstream commit fa3a419d2f674b431d38748cb58fb7da17ee8949 ]
> 
> The call to of_parse_phandle returns a node pointer with refcount
> incremented thus it must be explicitly decremented after the last
> usage.
> 
> Detected by coccinelle with the following warnings:
> ./drivers/net/ethernet/xilinx/xilinx_axienet_main.c:1624:1-7: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 1569, but without a corresponding object release within this function.
> 
> Signed-off-by: Wen Yang <wen.yang99@....com.cn>
> Cc: Anirudha Sarangi <anirudh@...inx.com>
> Cc: John Linn <John.Linn@...inx.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Michal Simek <michal.simek@...inx.com>
> Cc: netdev@...r.kernel.org
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: David S. Miller <davem@...emloft.net>
> Signed-off-by: Sasha Levin (Microsoft) <sashal@...nel.org>

Bug is real, but fix is horrible. This already uses gotos for error
handling, so use them....

This fixes it up.

Plus... I do not think these "of_node_put" fixes belong in
stable. They are theoretical bugs; so we hold reference to device tree
structure. a) it is small, b) it stays in memory, anyway. This does
not fix any real problem.

								Pavel


diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
index 4041c75..490d440 100644
--- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
@@ -1575,15 +1575,13 @@ static int axienet_probe(struct platform_device *pdev)
 	ret = of_address_to_resource(np, 0, &dmares);
 	if (ret) {
 		dev_err(&pdev->dev, "unable to get DMA resource\n");
-		of_node_put(np);
-		goto free_netdev;
+		goto free_netdev_put;
 	}
 	lp->dma_regs = devm_ioremap_resource(&pdev->dev, &dmares);
 	if (IS_ERR(lp->dma_regs)) {
 		dev_err(&pdev->dev, "could not map DMA regs\n");
 		ret = PTR_ERR(lp->dma_regs);
-		of_node_put(np);
-		goto free_netdev;
+		goto free_netdev_put;
 	}
 	lp->rx_irq = irq_of_parse_and_map(np, 1);
 	lp->tx_irq = irq_of_parse_and_map(np, 0);
@@ -1620,6 +1618,8 @@ static int axienet_probe(struct platform_device *pdev)
 
 	return 0;
 
+free_netdev_put:
+	of_node_put(np);
 free_netdev:
 	free_netdev(ndev);
 


> ---
>  drivers/net/ethernet/xilinx/xilinx_axienet_main.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> index f24f48f33802..7cfd7ff38e86 100644
> --- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> +++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> @@ -1574,12 +1574,14 @@ static int axienet_probe(struct platform_device *pdev)
>  	ret = of_address_to_resource(np, 0, &dmares);
>  	if (ret) {
>  		dev_err(&pdev->dev, "unable to get DMA resource\n");
> +		of_node_put(np);
>  		goto free_netdev;
>  	}
>  	lp->dma_regs = devm_ioremap_resource(&pdev->dev, &dmares);
>  	if (IS_ERR(lp->dma_regs)) {
>  		dev_err(&pdev->dev, "could not map DMA regs\n");
>  		ret = PTR_ERR(lp->dma_regs);
> +		of_node_put(np);
>  		goto free_netdev;
>  	}
>  	lp->rx_irq = irq_of_parse_and_map(np, 1);

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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