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Subject[PATCH] vma_adjust adjust_next wrap
Fix vma_adjust adjust_next wrapping: Rajesh V. pointed out that if end
were 2GB or more beyond next->vm_start (on 32-bit), then next->vm_pgoff
would have been negatively adjusted.

Signed-off-by: Hugh Dickins <hugh@veritas.com>

mm/mmap.c | 27 +++++++++++++++++----------
1 files changed, 17 insertions(+), 10 deletions(-)

--- 2.6.7-rc2/mm/mmap.c 2004-05-30 11:36:40.000000000 +0100
+++ linux/mm/mmap.c 2004-06-02 16:31:44.190703744 +0100
@@ -373,20 +373,27 @@ void vma_adjust(struct vm_area_struct *v

if (next && !insert) {
if (end >= next->vm_end) {
+ /*
+ * vma expands, overlapping all the next, and
+ * perhaps the one after too (mprotect case 6).
+ */
again: remove_next = 1 + (end > next->vm_end);
end = next->vm_end;
anon_vma = next->anon_vma;
- } else if (end < vma->vm_end || end > next->vm_start) {
+ } else if (end > next->vm_start) {
/*
- * vma shrinks, and !insert tells it's not
- * split_vma inserting another: so it must
- * be mprotect shifting the boundary down.
- * Or:
* vma expands, overlapping part of the next:
- * must be mprotect shifting the boundary up.
+ * mprotect case 5 shifting the boundary up.
+ */
+ adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
+ anon_vma = next->anon_vma;
+ } else if (end < vma->vm_end) {
+ /*
+ * vma shrinks, and !insert tells it's not
+ * split_vma inserting another: so it must be
+ * mprotect case 4 shifting the boundary down.
*/
- BUG_ON(vma->vm_end != next->vm_start);
- adjust_next = end - next->vm_start;
+ adjust_next = - ((vma->vm_end - end) >> PAGE_SHIFT);
anon_vma = next->anon_vma;
}
}
@@ -418,8 +425,8 @@ again: remove_next = 1 + (end > next->
vma->vm_end = end;
vma->vm_pgoff = pgoff;
if (adjust_next) {
- next->vm_start += adjust_next;
- next->vm_pgoff += adjust_next >> PAGE_SHIFT;
+ next->vm_start += adjust_next << PAGE_SHIFT;
+ next->vm_pgoff += adjust_next;
}

if (root) {
-
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