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Date: Thu, 10 Mar 2011 15:54:18 -0800 From: Greg KH <gregkh@...e.de> To: linux-kernel@...r.kernel.org, stable@...nel.org Cc: stable-review@...nel.org, torvalds@...ux-foundation.org, akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk, Hugh Dickins <hughd@...gle.com>, Kerin Millar <kerframil@...il.com> Subject: [patch 12/29] mm: fix possible cause of a page_mapped BUG 2.6.37-stable review patch. If anyone has any objections, please let us know. ------------------ From: Hugh Dickins <hughd@...gle.com> 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 <hughd@...gle.com> Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Kerin Millar <kerframil@...il.com> Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de> --- mm/mremap.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/mm/mremap.c +++ b/mm/mremap.c @@ -91,9 +91,7 @@ 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; } /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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