[PATCH] Modify the check condition

[cgel.zte@gmail.com]

From: Yang Guang <yang.guang5@zte.com.cn>

The vma may be NULL, and accessing the member of vma like "vma->vm_start"
in calling follow_phys may occur segmentation fault.
So it should check vma at beginning. If vma is null, it will return. And
the if condition won't execute "vm->vm_flags".

Signed-off-by: Yang Guang <yang.guang5@zte.com.cn>
---
 arch/x86/mm/pat/memtype.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c
index 4ba2a3ee4bce..b7108b37b754 100644
--- a/arch/x86/mm/pat/memtype.c
+++ b/arch/x86/mm/pat/memtype.c
@@ -1089,7 +1089,7 @@ void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
 	resource_size_t paddr;
 	unsigned long prot;
 
-	if (vma && !(vma->vm_flags & VM_PAT))
+	if (!(vma) || !(vma->vm_flags & VM_PAT))
 		return;
 
 	/* free the chunk starting from pfn or the whole chunk */
-- 
2.25.1