fix checks for expand-in-place mremap

Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 11 insertions, 2 deletions

diff --git a/mm/mremap.c b/mm/mremap.c
index 90e422c9f410..9d0753983dcb 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -27,6 +27,10 @@
 
 #include "internal.h"
 
+#ifndef arch_mmap_check
+#define arch_mmap_check(addr, len, flags)       (0)
+#endif
+
 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
 {
         pgd_t *pgd;
@@ -368,12 +372,17 @@ out:
 
 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
 {
+        unsigned long end = vma->vm_end + delta;
         unsigned long max_addr = TASK_SIZE;
         if (vma->vm_next)
                 max_addr = vma->vm_next->vm_start;
-        if (max_addr - vma->vm_end < delta)
+        if (max_addr < end || end < vma->vm_end)
+                return 0;
+        if (arch_mmap_check(vma->vm_start, end - vma->vm_start, MAP_FIXED))
+                return 0;
+        if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
+                              0, MAP_FIXED) & ~PAGE_MASK)
                 return 0;
-        /* we need to do arch-specific checks here */
         return 1;
 }