[POWERPC] Fix bogus BUG_ON() in in hugetlb_get_unmapped_area()

The powerpc specific version of hugetlb_get_unmapped_area() makes some
unwarranted assumptions about what checks have been made to its
parameters by its callers.  This will lead to a BUG_ON() if a 32-bit
process attempts to make a hugepage mapping which extends above
TASK_SIZE (4GB).

I'm not sure if these assumptions came about because they were valid
with earlier versions of the get_unmapped_area() path, or if it was
always broken.  Nonetheless this patch fixes the logic, and removes
the crash.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 89c836d54809..1bb20d841080 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -744,7 +744,8 @@ static int htlb_check_hinted_area(unsigned long addr, unsigned long len)
         struct vm_area_struct *vma;
 
         vma = find_vma(current->mm, addr);
-        if (!vma || ((addr + len) <= vma->vm_start))
+        if (TASK_SIZE - len >= addr &&
+            (!vma || ((addr + len) <= vma->vm_start)))
                 return 0;
 
         return -ENOMEM;
@@ -815,6 +816,8 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
                 return -EINVAL;
         if (len & ~HPAGE_MASK)
                 return -EINVAL;
+        if (len > TASK_SIZE)
+                return -ENOMEM;
 
         if (!cpu_has_feature(CPU_FTR_16M_PAGE))
                 return -EINVAL;
@@ -823,9 +826,6 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
         BUG_ON((addr + len)  < addr);
 
         if (test_thread_flag(TIF_32BIT)) {
-                /* Paranoia, caller should have dealt with this */
-                BUG_ON((addr + len) > 0x100000000UL);
-
                 curareas = current->mm->context.low_htlb_areas;
 
                 /* First see if we can use the hint address */