[PATCH] gsync: Avoid NULL pointer dereference

[Brent Baccala]

Hi -

Here's another gsync patch, to avoid kernel panics if the task port
passed in isn't actually a task port, in which case TASK_NULL is
passed as the task argument.

    agape
    brent

-- >8 --
Subject: [PATCH] gsync: Avoid NULL pointer dereference

* kern/gsync.c (gsync_wait, gsync_wake, gsync_requeue):
Return immediately if task argument is TASK_NULL
---
 kern/gsync.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/kern/gsync.c b/kern/gsync.c
index adb6e6e..e70e119 100644
--- a/kern/gsync.c
+++ b/kern/gsync.c
@@ -185,12 +185,13 @@ gsync_find_key (const struct list *entries,
 kern_return_t gsync_wait (task_t task, vm_offset_t addr,
   unsigned int lo, unsigned int hi, natural_t msec, int flags)
 {
-  struct gsync_waiter w;
-  int bucket = gsync_fill_key (task, addr, flags, &w.key);
-
   if (unlikely (task != current_task()))
     /* Not implemented yet.  */
     return (KERN_FAILURE);
+
+  struct gsync_waiter w;
+  int bucket = gsync_fill_key (task, addr, flags, &w.key);
+
   if (unlikely (bucket < 0))
     return (KERN_INVALID_ADDRESS);
 
@@ -280,12 +281,13 @@ dequeue_waiter (struct list *nodep)
 kern_return_t gsync_wake (task_t task,
   vm_offset_t addr, unsigned int val, int flags)
 {
-  struct gsync_key key;
-  int bucket = gsync_fill_key (task, addr, flags, &key);
-
   if (unlikely (task != current_task()))
     /* Not implemented yet.  */
     return (KERN_FAILURE);
+
+  struct gsync_key key;
+  int bucket = gsync_fill_key (task, addr, flags, &key);
+
   if (unlikely (bucket < 0))
     return (KERN_INVALID_ADDRESS);
 
@@ -330,13 +332,14 @@ kern_return_t gsync_wake (task_t task,
 kern_return_t gsync_requeue (task_t task, vm_offset_t src,
   vm_offset_t dst, boolean_t wake_one, int flags)
 {
+  if (unlikely (task != current_task()))
+    /* Not implemented yet.  */
+    return (KERN_FAILURE);
+
   struct gsync_key src_k, dst_k;
   int src_bkt = gsync_fill_key (task, src, flags, &src_k);
   int dst_bkt = gsync_fill_key (task, dst, flags, &dst_k);
 
-  if (unlikely (task != current_task()))
-    /* Not implemented yet.  */
-    return (KERN_FAILURE);
   if ((src_bkt | dst_bkt) < 0)
     return (KERN_INVALID_ADDRESS);
 
-- 
2.7.4