2.6.35-longterm review patch. If anyone has any objections, please let me know.
------------------ 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]> Signed-off-by: Andi Kleen <[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(-) Index: linux-2.6.35.y/mm/mremap.c =================================================================== --- linux-2.6.35.y.orig/mm/mremap.c 2011-03-29 22:50:52.769908168 -0700 +++ linux-2.6.35.y/mm/mremap.c 2011-03-29 23:03:01.920251035 -0700 @@ -91,9 +91,7 @@ */ 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; } /* _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
