1 files changed, 18 insertions, 8 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 9da8cab1b1b0..b623a249918c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1410,6 +1410,13 @@ no_page_table:
         return page;
 }
 
+static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
+{
+        return (vma->vm_flags & VM_GROWSDOWN) &&
+                (vma->vm_start == addr) &&
+                !vma_stack_continue(vma->vm_prev, addr);
+}
+
 /**
  * __get_user_pages() - pin user pages in memory
  * @tsk:        task_struct of target task
@@ -1488,7 +1495,6 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                 vma = find_extend_vma(mm, start);
                 if (!vma && in_gate_area(mm, start)) {
                         unsigned long pg = start & PAGE_MASK;
-                        struct vm_area_struct *gate_vma = get_gate_vma(mm);
                         pgd_t *pgd;
                         pud_t *pud;
                         pmd_t *pmd;
@@ -1513,10 +1519,11 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                                 pte_unmap(pte);
                                 return i ? : -EFAULT;
                         }
+                        vma = get_gate_vma(mm);
                         if (pages) {
                                 struct page *page;
 
-                                page = vm_normal_page(gate_vma, start, *pte);
+                                page = vm_normal_page(vma, start, *pte);
                                 if (!page) {
                                         if (!(gup_flags & FOLL_DUMP) &&
                                              is_zero_pfn(pte_pfn(*pte)))
@@ -1530,12 +1537,7 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                                 get_page(page);
                         }
                         pte_unmap(pte);
-                        if (vmas)
-                                vmas[i] = gate_vma;
-                        i++;
-                        start += PAGE_SIZE;
-                        nr_pages--;
-                        continue;
+                        goto next_page;
                 }
 
                 if (!vma ||
@@ -1549,6 +1551,13 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                         continue;
                 }
 
+                /*
+                 * If we don't actually want the page itself,
+                 * and it's the stack guard page, just skip it.
+                 */
+                if (!pages && stack_guard_page(vma, start))
+                        goto next_page;
+
                 do {
                         struct page *page;
                         unsigned int foll_flags = gup_flags;
@@ -1631,6 +1640,7 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                                 flush_anon_page(vma, page, start);
                                 flush_dcache_page(page);
                         }
+next_page:
                         if (vmas)
                                 vmas[i] = vma;
                         i++;