ahci: fix Null pointer dereference in achi_host_active()

commit b29900e6 (AHCI: Make distinct names for ports in /proc/interrupts)
introuded a regression, which resulted Null pointer dereference for achi
host with dummy ports. For ahci ports, when the port is dummy port, its
private_data will be NULL, as ata_dummy_port_ops doesn't support ->port_start.

changes in v2: use pp to check dummy ports, update comments

Reported-and-tested-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Xiaotian Feng <xtfeng@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Alexander Gordeev <agordeev@redhat.com>
Cc: linux-ide@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

1 files changed, 8 insertions, 1 deletions

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 5064f3ea20f1..db4380d70031 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -1146,11 +1146,18 @@ int ahci_host_activate(struct ata_host *host, int irq, unsigned int n_msis)
                 return rc;
 
         for (i = 0; i < host->n_ports; i++) {
+                const char* desc;
                 struct ahci_port_priv *pp = host->ports[i]->private_data;
 
+                /* pp is NULL for dummy ports */
+                if (pp)
+                        desc = pp->irq_desc;
+                else
+                        desc = dev_driver_string(host->dev);
+
                 rc = devm_request_threaded_irq(host->dev,
                         irq + i, ahci_hw_interrupt, ahci_thread_fn, IRQF_SHARED,
-                        pp->irq_desc, host->ports[i]);
+                        desc, host->ports[i]);
                 if (rc)
                         goto out_free_irqs;
         }