mm: fix ia64 crash when gcore reads gate area

[net-next-2.6.git] / mm / memory.c

diff --git a/mm/memory.c b/mm/memory.c
index 833952d8b74d3a8ec8a3750bf664dba2d02671ed..bde42c6d3633f15cfe51b1eae8e3e56833e86955 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1227,8 +1227,17 @@ int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
 }
 EXPORT_SYMBOL_GPL(zap_vma_ptes);
 
-/*
- * Do a quick page-table lookup for a single page.
+/**
+ * follow_page - look up a page descriptor from a user-virtual address
+ * @vma: vm_area_struct mapping @address
+ * @address: virtual address to look up
+ * @flags: flags modifying lookup behaviour
+ *
+ * @flags can have FOLL_ flags set, defined in <linux/mm.h>
+ *
+ * Returns the mapped (struct page *), %NULL if no mapping exists, or
+ * an error pointer if there is a mapping to something not represented
+ * by a page descriptor (see also vm_normal_page()).
  */
 struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
                        unsigned int flags)
@@ -1385,10 +1394,20 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                                return i ? : -EFAULT;
                        }
                        if (pages) {
-                               struct page *page = vm_normal_page(gate_vma, start, *pte);
+                               struct page *page;
+
+                               page = vm_normal_page(gate_vma, start, *pte);
+                               if (!page) {
+                                       if (!(gup_flags & FOLL_DUMP) &&
+                                            is_zero_pfn(pte_pfn(*pte)))
+                                               page = pte_page(*pte);
+                                       else {
+                                               pte_unmap(pte);
+                                               return i ? : -EFAULT;
+                                       }
+                               }
                                pages[i] = page;
-                               if (page)
-                                       get_page(page);
+                               get_page(page);
                        }
                        pte_unmap(pte);
                        if (vmas)