linux-kernel - Re: [PATCH v2] isdn: hfcpci: fix potential NULL pointer dereference

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Message-Id: <20190311.121412.1771390861732982560.davem@davemloft.net>
Date:   Mon, 11 Mar 2019 12:14:12 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     kjlu@....edu
Cc:     pakki001@....edu, isdn@...ux-pingi.de, gustavo@...eddedor.com,
        baijiaju1990@...il.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] isdn: hfcpci: fix potential NULL pointer dereference

From: Kangjie Lu <kjlu@....edu>
Date: Mon, 11 Mar 2019 00:34:34 -0500

> In case ioremap fails, the fix releases resources and returns.
> 
> Signed-off-by: Kangjie Lu <kjlu@....edu>
> ---
>  drivers/isdn/hardware/mISDN/hfcpci.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/isdn/hardware/mISDN/hfcpci.c b/drivers/isdn/hardware/mISDN/hfcpci.c
> index ebb3fa2e1d00..d1d53c5de3c0 100644
> --- a/drivers/isdn/hardware/mISDN/hfcpci.c
> +++ b/drivers/isdn/hardware/mISDN/hfcpci.c
> @@ -2036,6 +2036,12 @@ setup_hw(struct hfc_pci *hc)
>  	       "HFC-PCI: defined at mem %#lx fifo %#lx(%#lx) IRQ %d HZ %d\n",
>  	       (u_long) hc->hw.pci_io, (u_long) hc->hw.fifos,
>  	       (u_long) hc->hw.dmahandle, hc->irq, HZ);
> +	if (unlikely(!hc->hw.pci_io)) {
> +		pci_free_consistent(hc->pdev, 0x8000, hc->hw.fifos,
> +				    hc->hw.dmahandle);
> +		return 1;
> +	}

The log message emitted before this new check reports detection of the
device, which you should not do if we are going to fail the probe.