Messages in this thread Patch in this message | | | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH 1/1] mm: implement ->map_pages for shmem/tmpfs | Date | Mon, 3 Mar 2014 13:07:46 +0200 (EET) |
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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.shutemov@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 <hughd@google.com> Reported-by: Ning Qu <quning@google.com> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@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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