This is a note to let you know that I've just added the patch titled
mm: fix possible cause of a page_mapped BUG
to the 2.6.32-longterm tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/longterm/longterm-queue-2.6.32.git;a=summary
The filename of the patch is:
mm-fix-possible-cause-of-a-page_mapped-bug.patch
and it can be found in the queue-2.6.32 subdirectory.
If you, or anyone else, feels it should not be added to the 2.6.32 longterm
tree,
please let <[email protected]> know about it.
>From a3e8cc643d22d2c8ed36b9be7d9c9ca21efcf7f7 Mon Sep 17 00:00:00 2001
From: Hugh Dickins <[email protected]>
Date: Wed, 23 Feb 2011 21:39:49 -0800
Subject: mm: fix possible cause of a page_mapped BUG
From: Hugh Dickins <[email protected]>
commit a3e8cc643d22d2c8ed36b9be7d9c9ca21efcf7f7 upstream.
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 <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Cc: Kerin Millar <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
mm/mremap.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -92,9 +92,7 @@ static void move_ptes(struct vm_area_str
*/
mapping = vma->vm_file->f_mapping;
spin_lock(&mapping->i_mmap_lock);
- 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;
}
/*
Patches currently in longterm-queue-2.6.32 which might be from [email protected]
are
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