linux-kernel - Re: [PATCH v2] pci: pcie-xilinx: fix a missing-check bug for __get_free_pages

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Message-ID: <20190325215105.GB24180@google.com>
Date:   Mon, 25 Mar 2019 16:51:06 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Kangjie Lu <kjlu@....edu>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        linux-pci@...r.kernel.org, Michal Simek <michal.simek@...inx.com>,
        linux-kernel@...r.kernel.org, pakki001@....edu,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] pci: pcie-xilinx: fix a missing-check bug for
 __get_free_pages

Hi Kangjie,

Thanks for the patch!

Please update the subject line like this:

  PCI: xilinx: Check for __get_free_pages() failure

You can always get a good idea of the style for subject lines by doing
something like this:

  git log --oneline --follow drivers/pci/controller/pcie-xilinx.c

On Mon, Mar 25, 2019 at 04:31:13PM -0500, Kangjie Lu wrote:
> In case __get_free_pages fail, the fix returns -ENOMEMto avoid
> NULL pointer dereference.

s/In case/If/
s/__get_free_pages/__get_free_pages()/
s/fail/fails/
s/the fix returns/return/
s/-ENOMEMto/-ENOMEM to/

> Signed-off-by: Kangjie Lu <kjlu@....edu>
> Reviewed-by: Steven Price <steven.price@....com>

I didn't see Steven's reviewed-by on the mailing list.  I did see his
*review*, but his "Reviewed-by: Steven Price <steven.price@....com>"
implies that he reviewed it *and* believes it to ready for merging
(see Documentation/process/submitting-patches.rst for all the
details).

So we should only add the Reviewed-by tag after Steven himself posts
it.

> ---
> v2: caller is redefined to accept the error code, as suggested by
> Steven Price <steven.price@....com>
> ---
>  drivers/pci/controller/pcie-xilinx.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/pcie-xilinx.c b/drivers/pci/controller/pcie-xilinx.c
> index 9bd1a35cd5d8..abc214e94f7c 100644
> --- a/drivers/pci/controller/pcie-xilinx.c
> +++ b/drivers/pci/controller/pcie-xilinx.c
> @@ -336,14 +336,19 @@ static const struct irq_domain_ops msi_domain_ops = {
>   * xilinx_pcie_enable_msi - Enable MSI support
>   * @port: PCIe port information
>   */
> -static void xilinx_pcie_enable_msi(struct xilinx_pcie_port *port)
> +static int xilinx_pcie_enable_msi(struct xilinx_pcie_port *port)
>  {
>  	phys_addr_t msg_addr;
>  
>  	port->msi_pages = __get_free_pages(GFP_KERNEL, 0);
> +	if (unlikely(!port->msi_pages))
> +		return -ENOMEM;

No need to use "unlikely()" here.  It *is* unlikely that
__get_free_pages() will fail, but the annotation clutters the code a
bit, so I prefer to avoid it except for performance paths.

This should probably be documented somewhere in
Documentation/process/, but regrettably, it isn't (yet).

>  	msg_addr = virt_to_phys((void *)port->msi_pages);
>  	pcie_write(port, 0x0, XILINX_PCIE_REG_MSIBASE1);
>  	pcie_write(port, msg_addr, XILINX_PCIE_REG_MSIBASE2);
> +
> +	return 0;
>  }
>  
>  /* INTx Functions */
> @@ -498,6 +503,7 @@ static int xilinx_pcie_init_irq_domain(struct xilinx_pcie_port *port)
>  	struct device *dev = port->dev;
>  	struct device_node *node = dev->of_node;
>  	struct device_node *pcie_intc_node;
> +	int ret;
>  
>  	/* Setup INTx */
>  	pcie_intc_node = of_get_next_child(node, NULL);
> @@ -526,7 +532,9 @@ static int xilinx_pcie_init_irq_domain(struct xilinx_pcie_port *port)
>  			return -ENODEV;
>  		}
>  
> -		xilinx_pcie_enable_msi(port);
> +		ret = xilinx_pcie_enable_msi(port);
> +		if (ret)
> +			return ret;
>  	}
>  
>  	return 0;
> -- 
> 2.17.1
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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