[OPENPROMIO]: Handle current_node being NULL correctly.

If the user tries to traverse to the next node of the
last node, we get NULL in current_node and a zero phandle
returned.  That's fine, but if the user tries to obtain
properties in that state, we try to dereference a NULL
pointer in the downcall to the of_*() routines.

So protect against that.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 3 deletions

diff --git a/drivers/sbus/char/openprom.c b/drivers/sbus/char/openprom.c
index 293bb2fdb1d5..2f698763ba5d 100644
--- a/drivers/sbus/char/openprom.c
+++ b/drivers/sbus/char/openprom.c
@@ -145,8 +145,9 @@ static int opromgetprop(void __user *argp, struct device_node *dp, struct openpr
         void *pval;
         int len;
 
-        pval = of_get_property(dp, op->oprom_array, &len);
-        if (!pval || len <= 0 || len > bufsize)
+        if (!dp ||
+            !(pval = of_get_property(dp, op->oprom_array, &len)) ||
+            len <= 0 || len > bufsize)
                 return copyout(argp, op, sizeof(int));
 
         memcpy(op->oprom_array, pval, len);
@@ -161,6 +162,8 @@ static int opromnxtprop(void __user *argp, struct device_node *dp, struct openpr
         struct property *prop;
         int len;
 
+        if (!dp)
+                return copyout(argp, op, sizeof(int));
         if (op->oprom_array[0] == '\0') {
                 prop = dp->properties;
                 if (!prop)
@@ -266,9 +269,13 @@ static int oprompci2node(void __user *argp, struct device_node *dp, struct openp
 
 static int oprompath2node(void __user *argp, struct device_node *dp, struct openpromio *op, int bufsize, DATA *data)
 {
+        phandle ph = 0;
+
         dp = of_find_node_by_path(op->oprom_array);
+        if (dp)
+                ph = dp->node;
         data->current_node = dp;
-        *((int *)op->oprom_array) = dp->node;
+        *((int *)op->oprom_array) = ph;
         op->oprom_size = sizeof(int);
 
         return copyout(argp, op, bufsize + sizeof(int));