[PATCH] ata: libata-core: fix NULL pointer deref in ata_host_alloc_pinfo()

[Sergey Shtylyov <s.shtylyov@omp.ru>]

In an unlikely (and probably wrong?) case that the 'ppi' parameter of
ata_host_alloc_pinfo() points to an array starting with a NULL pointer,
there's going to be a kernel oops as the 'pi' local variable won't get
reassigned from the initial value of NULL.  Assign &ata_dummy_port_info
to 'pi' at the start of the *for* loop instead to fix this kernel oops
for good...

Found by Linux Verification Center (linuxtesting.org) with the SVACE static
analysis tool.

Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>

---
This patch is against the 'for-next' branch of Damien's 'libata.git' repo.

 drivers/ata/libata-core.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: libata/drivers/ata/libata-core.c
===================================================================
--- libata.orig/drivers/ata/libata-core.c
+++ libata/drivers/ata/libata-core.c
@@ -5470,7 +5470,7 @@ struct ata_host *ata_host_alloc_pinfo(st
 	if (!host)
 		return NULL;
 
-	for (i = 0, j = 0, pi = NULL; i < host->n_ports; i++) {
+	for (i = 0, j = 0, pi = &ata_dummy_port_info; i < host->n_ports; i++) {
 		struct ata_port *ap = host->ports[i];
 
 		if (ppi[j])