From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Fri, 19 Oct 2012 20:37:57 +0000 (-0700)
Subject: remap_file_pages: correctly handle the case of a NULL vm_ops pointer
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=deb521c44fa529b24cc78a64702757a683f82487;p=openwrt%2Fstaging%2Fblogic.git

remap_file_pages: correctly handle the case of a NULL vm_ops pointer

In commit 0b173bc4daa8 ("mm: kill vma flag VM_CAN_NONLINEAR") we
replaced the VM_CAN_NONLINEAR test with checking whether the mapping has
a '->remap_pages()' vm operation, but there is no guarantee that there
it even has a vm_ops pointer at all.

Add the appropriate test for NULL vm_ops.

Reported-by: Sasha Levin <levinsasha928@gmail.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/fremap.c b/mm/fremap.c
index 3899a86851ce..a0aaf0e56800 100644
--- a/mm/fremap.c
+++ b/mm/fremap.c
@@ -169,7 +169,7 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
 	if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
 		goto out;
 
-	if (!vma->vm_ops->remap_pages)
+	if (!vma->vm_ops || !vma->vm_ops->remap_pages)
 		goto out;
 
 	if (start < vma->vm_start || start + size > vma->vm_end)