fix NULL pointer dereference in __vm_enough_memory()

The new exec code inserts an accounted vma into an mm struct which is not
current->mm.  The existing memory check code has a hard coded assumption
that this does not happen as does the security code.

As the correct mm is known we pass the mm to the security method and the
helper function.  A new security test is added for the case where we need
to pass the mm and the existing one is modified to pass current->mm to
avoid the need to change large amounts of code.

(Thanks to Tobias for fixing rejects and testing)

Signed-off-by: Alan Cox <alan@redhat.com>
Cc: WU Fengguang <wfg@mail.ustc.edu.cn>
Cc: James Morris <jmorris@redhat.com>
Cc: Tobias Diedrich <ranma+kernel@tdiedrich.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 4 insertions, 4 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
index b6537211b9cc..0d40e66c841b 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -93,7 +93,7 @@ atomic_t vm_committed_space = ATOMIC_INIT(0);
  * Note this is a helper function intended to be used by LSMs which
  * wish to use this logic.
  */
-int __vm_enough_memory(long pages, int cap_sys_admin)
+int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
 {
         unsigned long free, allowed;
 
@@ -166,7 +166,7 @@ int __vm_enough_memory(long pages, int cap_sys_admin)
 
         /* Don't let a single process grow too big:
            leave 3% of the size of this process for other processes */
-        allowed -= current->mm->total_vm / 32;
+        allowed -= mm->total_vm / 32;
 
         /*
          * cast `allowed' as a signed long because vm_committed_space
@@ -2077,7 +2077,7 @@ int insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma)
         if (__vma && __vma->vm_start < vma->vm_end)
                 return -ENOMEM;
         if ((vma->vm_flags & VM_ACCOUNT) &&
-             security_vm_enough_memory(vma_pages(vma)))
+             security_vm_enough_memory_mm(mm, vma_pages(vma)))
                 return -ENOMEM;
         vma_link(mm, vma, prev, rb_link, rb_parent);
         return 0;
diff --git a/mm/nommu.c b/mm/nommu.c
index 9eef6a398555..8ed0cb43118a 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1270,7 +1270,7 @@ EXPORT_SYMBOL(get_unmapped_area);
  * Note this is a helper function intended to be used by LSMs which
  * wish to use this logic.
  */
-int __vm_enough_memory(long pages, int cap_sys_admin)
+int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
 {
         unsigned long free, allowed;