diff options
authorHugh Dickins <>2011-02-23 21:39:49 -0800
committerLinus Torvalds <>2011-02-23 21:55:06 -0800
commita3e8cc643d22d2c8ed36b9be7d9c9ca21efcf7f7 (patch)
parent2aa15890f3c191326678f1bd68af61ec6b8753ec (diff)
mm: fix possible cause of a page_mapped BUG
Robert Swiecki reported a BUG_ON(page_mapped) from a fuzzer, punching a hole with madvise(,, MADV_REMOVE). That path is under mutex, and cannot be explained by lack of serialization in unmap_mapping_range(). Reviewing the code, I found one place where vm_truncate_count handling should have been updated, when I switched at the last minute from one way of managing the restart_addr to another: mremap move changes the virtual addresses, so it ought to adjust the restart_addr. But rather than exporting the notion of restart_addr from memory.c, or converting to restart_pgoff throughout, simply reset vm_truncate_count to 0 to force a rescan if mremap move races with preempted truncation. We have no confirmation that this fixes Robert's BUG, but it is a fix that's worth making anyway. Signed-off-by: Hugh Dickins <> Signed-off-by: Linus Torvalds <>
1 files changed, 1 insertions, 3 deletions
diff --git a/mm/mremap.c b/mm/mremap.c
index 9925b6391b80..1de98d492ddc 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -94,9 +94,7 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
mapping = vma->vm_file->f_mapping;
- if (new_vma->vm_truncate_count &&
- new_vma->vm_truncate_count != vma->vm_truncate_count)
- new_vma->vm_truncate_count = 0;
+ new_vma->vm_truncate_count = 0;