Ning Qu wrote:
> Btw, should we first check if page returned by radix_tree_deref_slot is NULL?
Yes, we should. I don't know how I missed that. :(
The patch below should address both issues.
>From dca24c9a1f31ee1599fe81e9a60d4f87a4eaf0ea Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shute...@linux.intel.com>
Date: Mon, 3 Mar 2014 12:07:03 +0200
Subject: [PATCH] mm: filemap_map_pages() avoid dereference NULL/exception
slots
radix_tree_deref_slot() can return NULL: add missed check.
Do no dereference 'page': we can get there as result of
radix_tree_exception(page) check.
Reported-by: Hugh Dickins <hu...@google.com>
Reported-by: Ning Qu <qun...@google.com>
Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
---
mm/filemap.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index 5f4fe7f0c258..e48624634927 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1745,6 +1745,8 @@ void filemap_map_pages(struct vm_area_struct *vma, struct
vm_fault *vmf)
break;
repeat:
page = radix_tree_deref_slot(slot);
+ if (unlikely(!page))
+ goto next;
if (radix_tree_exception(page)) {
if (radix_tree_deref_retry(page))
break;
@@ -1790,7 +1792,7 @@ unlock:
skip:
page_cache_release(page);
next:
- if (page->index == vmf->max_pgoff)
+ if (iter.index == vmf->max_pgoff)
break;
}
rcu_read_unlock();
--
Kirill A. Shutemov
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