From f6f490252259e239288ae121d8f0e845f6cd1a22 Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Wed, 23 Jul 2014 14:00:08 -0700 Subject: mm: do not call do_fault_around for non-linear fault commit c118678bc79e8241f9d3434d9324c6400d72f48a upstream. Ingo Korb reported that "repeated mapping of the same file on tmpfs using remap_file_pages sometimes triggers a BUG at mm/filemap.c:202 when the process exits". He bisected the bug to d7c1755179b8 ("mm: implement ->map_pages for shmem/tmpfs"), although the bug was actually added by commit 8c6e50b0290c ("mm: introduce vm_ops->map_pages()"). The problem is caused by calling do_fault_around for a _non-linear_ fault. In this case pgoff is shifted and might become negative during calculation. Faulting around non-linear page-fault makes no sense and breaks the logic in do_fault_around because pgoff is shifted. Signed-off-by: Konstantin Khlebnikov Reported-by: Ingo Korb Tested-by: Ingo Korb Cc: Hugh Dickins Cc: Sasha Levin Cc: Dave Jones Cc: Ning Qu Cc: "Kirill A. Shutemov" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/memory.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/memory.c b/mm/memory.c index e302ae1dcce..4f9e53024b2 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3515,7 +3515,7 @@ static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma, * if page by the offset is not ready to be mapped (cold cache or * something). */ - if (vma->vm_ops->map_pages) { + if (vma->vm_ops->map_pages && !(flags & FAULT_FLAG_NONLINEAR)) { pte = pte_offset_map_lock(mm, pmd, address, &ptl); do_fault_around(vma, address, pte, pgoff, flags); if (!pte_same(*pte, orig_pte)) -- cgit v1.2.3-18-g5258