[PATCH] powerpc/booke: Only check for hugetlb in flush if vma != NULL

[Scott Wood]

And in flush_hugetlb_page(), don't check whether vma is NULL after
we've already dereferenced it.

This was found by Dan using static analysis as described here:
https://lists.ozlabs.org/pipermail/linuxppc-dev/2013-November/113161.html

We currently get away with this because the callers that currently pass
NULL for vma seem to be 32-bit-only (e.g. highmem, and
CONFIG_DEBUG_PGALLOC in pgtable_32.c)  Hugetlb is currently 64-bit only,
so we never saw a NULL vma here.

Signed-off-by: Scott Wood <scottwood at freescale.com>
Reported-by: Dan Carpenter <dan.carpenter at oracle.com>
---
 arch/powerpc/mm/hugetlbpage-book3e.c | 3 +--
 arch/powerpc/mm/tlb_nohash.c         | 2 +-
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/mm/hugetlbpage-book3e.c b/arch/powerpc/mm/hugetlbpage-book3e.c
index 3bc7006..74551b5 100644
--- a/arch/powerpc/mm/hugetlbpage-book3e.c
+++ b/arch/powerpc/mm/hugetlbpage-book3e.c
@@ -117,6 +117,5 @@ void flush_hugetlb_page(struct vm_area_struct *vma, unsigned long vmaddr)
 	struct hstate *hstate = hstate_file(vma->vm_file);
 	unsigned long tsize = huge_page_shift(hstate) - 10;
 
-	__flush_tlb_page(vma ? vma->vm_mm : NULL, vmaddr, tsize, 0);
-
+	__flush_tlb_page(vma->vm_mm, vmaddr, tsize, 0);
 }
diff --git a/arch/powerpc/mm/tlb_nohash.c b/arch/powerpc/mm/tlb_nohash.c
index 41cd68d..358d743 100644
--- a/arch/powerpc/mm/tlb_nohash.c
+++ b/arch/powerpc/mm/tlb_nohash.c
@@ -305,7 +305,7 @@ void __flush_tlb_page(struct mm_struct *mm, unsigned long vmaddr,
 void flush_tlb_page(struct vm_area_struct *vma, unsigned long vmaddr)
 {
 #ifdef CONFIG_HUGETLB_PAGE
-	if (is_vm_hugetlb_page(vma))
+	if (vma && is_vm_hugetlb_page(vma))
 		flush_hugetlb_page(vma, vmaddr);
 #endif
 
-- 
1.8.1.2