mm: use mm_struct to resolve gate vma's in __get_user_pages

We now check if a requested user page overlaps a gate vma using the supplied mm
instead of the supplied task.  The given task is now used solely for accounting
purposes and may be NULL.

Signed-off-by: Stephen Wilson <wilsons@start.ca>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 11 insertions, 7 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 5f5b5de5a40e..5f585b65d734 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1486,9 +1486,9 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                 struct vm_area_struct *vma;
 
                 vma = find_extend_vma(mm, start);
-                if (!vma && in_gate_area(tsk->mm, start)) {
+                if (!vma && in_gate_area(mm, start)) {
                         unsigned long pg = start & PAGE_MASK;
-                        struct vm_area_struct *gate_vma = get_gate_vma(tsk->mm);
+                        struct vm_area_struct *gate_vma = get_gate_vma(mm);
                         pgd_t *pgd;
                         pud_t *pud;
                         pmd_t *pmd;
@@ -1589,10 +1589,13 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                                                 return i ? i : -EFAULT;
                                         BUG();
                                 }
-                                if (ret & VM_FAULT_MAJOR)
-                                        tsk->maj_flt++;
-                                else
-                                        tsk->min_flt++;
+
+                                if (tsk) {
+                                        if (ret & VM_FAULT_MAJOR)
+                                                tsk->maj_flt++;
+                                        else
+                                                tsk->min_flt++;
+                                }
 
                                 if (ret & VM_FAULT_RETRY) {
                                         *nonblocking = 0;
@@ -1638,7 +1641,8 @@ EXPORT_SYMBOL(__get_user_pages);
 
 /**
  * get_user_pages() - pin user pages in memory
- * @tsk:        task_struct of target task
+ * @tsk:        the task_struct to use for page fault accounting, or
+ *              NULL if faults are not to be recorded.
  * @mm:         mm_struct of target mm
  * @start:      starting user address
  * @nr_pages:   number of pages from start to pin