linux-kernel - [patch] spi: rockchip: potential NULL dereference on error

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Message-ID: <20160504062546.GG22064@mwanda>
Date:	Wed, 4 May 2016 09:25:46 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Mark Brown <broonie@...nel.org>,
	Shawn Lin <shawn.lin@...k-chips.com>
Cc:	Heiko Stuebner <heiko@...ech.de>, linux-spi@...r.kernel.org,
	linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: [patch] spi: rockchip: potential NULL dereference on error

We were calling dma_release_channel(rs->dma_tx.ch) when "rs->dma_tx.ch"
is potentially NULL.  There is actually a call to that in the unwind
code at the bottom of the function so we can just re-arrange this a bit
and remove the call.  Also there is no need to set rs->dma_tx.ch to
NULL on this error path.

Fixes: e4c0e06f949b ('spi: rockchip: fix probe deferral handling')
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c
index 6c6c001..cd89682 100644
--- a/drivers/spi/spi-rockchip.c
+++ b/drivers/spi/spi-rockchip.c
@@ -744,10 +744,8 @@ static int rockchip_spi_probe(struct platform_device *pdev)
 	rs->dma_rx.ch = dma_request_chan(rs->dev, "rx");
 	if (IS_ERR(rs->dma_rx.ch)) {
 		if (PTR_ERR(rs->dma_rx.ch) == -EPROBE_DEFER) {
-			dma_release_channel(rs->dma_tx.ch);
-			rs->dma_tx.ch = NULL;
 			ret = -EPROBE_DEFER;
-			goto err_get_fifo_len;
+			goto err_free_dma_tx;
 		}
 		dev_warn(rs->dev, "Failed to request RX DMA channel\n");
 		rs->dma_rx.ch = NULL;
@@ -775,10 +773,11 @@ static int rockchip_spi_probe(struct platform_device *pdev)
 
 err_register_master:
 	pm_runtime_disable(&pdev->dev);
-	if (rs->dma_tx.ch)
-		dma_release_channel(rs->dma_tx.ch);
 	if (rs->dma_rx.ch)
 		dma_release_channel(rs->dma_rx.ch);
+err_free_dma_tx:
+	if (rs->dma_tx.ch)
+		dma_release_channel(rs->dma_tx.ch);
 err_get_fifo_len:
 	clk_disable_unprepare(rs->spiclk);
 err_spiclk_enable: