[PATCH] Check if start address is in vma region in NOMMU function get_user_pages()

In NOMMU arch, if run "cat /proc/self/mem", data from physical address 0
are read.  This behavior is different from MMU arch.  In IA32, message
"cat: /proc/self/mem: Input/output error" is reported.

This issue is rootcaused by not validate the start address in NOMMU
function get_user_pages().  Following patch solves this issue.

Signed-off-by: Sonic Zhang <sonic.adi@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/mm/nommu.c b/mm/nommu.c
index 00ffa974c90c..2af50831183f 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -129,16 +129,20 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
         struct page **pages, struct vm_area_struct **vmas)
 {
         int i;
-        static struct vm_area_struct dummy_vma;
+        struct vm_area_struct *vma;
 
         for (i = 0; i < len; i++) {
+                vma = find_vma(mm, start);
+                if(!vma)
+                        return i ? : -EFAULT;
+
                 if (pages) {
                         pages[i] = virt_to_page(start);
                         if (pages[i])
                                 page_cache_get(pages[i]);
                 }
                 if (vmas)
-                        vmas[i] = &dummy_vma;
+                        vmas[i] = vma;
                 start += PAGE_SIZE;
         }
         return(i);