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

[Robin Murphy]

On 23/03/2019 21:04, Aditya Pakki wrote:
In case __get_free_pages fail, the fix returns error upstream
to avoid NULL pointer dereference.

Where does msi_pages ever get dereferenced?

The logic here might actually still have a chance of working out OK with 
NULL depending on how the memory maps line up, but even if it doesn't, 
the problem is certainly not one of dereferencing.

Robin.

Signed-off-by: Aditya Pakki <pakki...@umn.edu>

---
v1: Return error upstream as suggested by Steven
---
  drivers/pci/controller/pcie-xilinx.c | 11 +++++++++--
  1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/pcie-xilinx.c 
b/drivers/pci/controller/pcie-xilinx.c
index 9bd1a35cd5d8..91d8945bfb0c 100644
--- a/drivers/pci/controller/pcie-xilinx.c
+++ b/drivers/pci/controller/pcie-xilinx.c
@@ -335,15 +335,19 @@ static const struct irq_domain_ops msi_domain_ops = {
  /**
   * xilinx_pcie_enable_msi - Enable MSI support
   * @port: PCIe port information
+ * Return: 0 on success, negative error on failure
   */
-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 (!port->msi_pages)
+               return -ENOMEM;
        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 +502,7 @@ 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 +531,9 @@ 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;