Don't allow the stack to grow into hugetlb reserved regions (CVE-2007-3739)

When expanding the stack, we don't currently check if the VMA will cross
into an area of the address space that is reserved for hugetlb pages.
Subsequent faults on the expanded portion of such a VMA will confuse the
low-level MMU code, resulting in an OOPS.  Check for this.

Signed-off-by: Adam Litke <agl@us.ibm.com>
Signed-off-by: Adrian Bunk <bunk@kernel.org>

diff --git a/mm/mmap.c b/mm/mmap.c
index fba355c065283091eff630d9719731ca6dced6b2..f2ac461a357e7ddccba91ffddf820740db35b2b3 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1460,6 +1460,7 @@ static int acct_stack_growth(struct vm_area_struct * vma, unsigned long size, un
 {
        struct mm_struct *mm = vma->vm_mm;
        struct rlimit *rlim = current->signal->rlim;
+       unsigned long new_start;
 
        /* address space limit tests */
        if (!may_expand_vm(mm, grow))
@@ -1479,6 +1480,12 @@ static int acct_stack_growth(struct vm_area_struct * vma, unsigned long size, un
                        return -ENOMEM;
        }
 
+       /* Check to ensure the stack will not grow into a hugetlb-only region */
+       new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
+                       vma->vm_end - size;
+       if (is_hugepage_only_range(vma->vm_mm, new_start, size))
+               return -EFAULT;
+
        /*
         * Overcommit..  This must be the final test, as it will
         * update security statistics.