linux-kernel - [PATCH v2] 8250_lpss: check null return when calling pci_ioremap

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Date:   Fri, 19 Jul 2019 12:48:45 -0500
From:   Navid Emamdoost <navid.emamdoost@...il.com>
To:     andriy.shevchenko@...ux.intel.com
Cc:     emamd001@....edu, kjlu@....edu, smccaman@....edu,
        Navid Emamdoost <navid.emamdoost@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, Vinod Koul <vkoul@...nel.org>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] 8250_lpss: check null return when calling pci_ioremap_bar

pci_ioremap_bar may return null. This is eventually de-referenced at 
drivers/dma/dw/core.c:1154 and drivers/dma/dw/core.c:1168. A null check 
is needed to prevent null de-reference. I am adding the check and in case
 of failure. Thanks to Andy Shevchenko for the hint on the necessity of 
pci_iounmap when exiting.

Signed-off-by: Navid Emamdoost <navid.emamdoost@...il.com>
---
 drivers/tty/serial/8250/8250_lpss.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_lpss.c b/drivers/tty/serial/8250/8250_lpss.c
index 53ca9ba6ab4b..d07e431110d9 100644
--- a/drivers/tty/serial/8250/8250_lpss.c
+++ b/drivers/tty/serial/8250/8250_lpss.c
@@ -169,10 +169,12 @@ static void qrk_serial_setup_dma(struct lpss8250 *lpss, struct uart_port *port)
 	struct pci_dev *pdev = to_pci_dev(port->dev);
 	int ret;
 
+	chip->pdata = &qrk_serial_dma_pdata;
 	chip->dev = &pdev->dev;
 	chip->irq = pci_irq_vector(pdev, 0);
 	chip->regs = pci_ioremap_bar(pdev, 1);
-	chip->pdata = &qrk_serial_dma_pdata;
+	if (!chip->regs)
+		return;
 
 	/* Falling back to PIO mode if DMA probing fails */
 	ret = dw_dma_probe(chip);
@@ -195,11 +197,15 @@ static void qrk_serial_setup_dma(struct lpss8250 *lpss, struct uart_port *port)
 
 static void qrk_serial_exit_dma(struct lpss8250 *lpss)
 {
+	struct dw_dma_chip *chip = &lpss->dma_chip;
 	struct dw_dma_slave *param = &lpss->dma_param;
 
 	if (!param->dma_dev)
 		return;
-	dw_dma_remove(&lpss->dma_chip);
+
+	dw_dma_remove(chip);
+
+	pci_iounmap(to_pci_dev(chip->dev), chip->regs);
 }
 #else	/* CONFIG_SERIAL_8250_DMA */
 static void qrk_serial_setup_dma(struct lpss8250 *lpss, struct uart_port *port) {}
-- 
2.17.1