3.13.11-ckt16 -stable review patch. If anyone has any objections, please let me know.
------------------ From: Konstantin Khlebnikov <[email protected]> commit b800c91a0517071156e772d4fb329ad33590da62 upstream. Fix for BUG_ON(anon_vma->degree) splashes in unlink_anon_vmas() ("kernel BUG at mm/rmap.c:399!") caused by commit 7a3ef208e662 ("mm: prevent endless growth of anon_vma hierarchy") Anon_vma_clone() is usually called for a copy of source vma in destination argument. If source vma has anon_vma it should be already in dst->anon_vma. NULL in dst->anon_vma is used as a sign that it's called from anon_vma_fork(). In this case anon_vma_clone() finds anon_vma for reusing. Vma_adjust() calls it differently and this breaks anon_vma reusing logic: anon_vma_clone() links vma to old anon_vma and updates degree counters but vma_adjust() overrides vma->anon_vma right after that. As a result final unlink_anon_vmas() decrements degree for wrong anon_vma. This patch assigns ->anon_vma before calling anon_vma_clone(). Signed-off-by: Konstantin Khlebnikov <[email protected]> Reported-and-tested-by: Chris Clayton <[email protected]> Reported-and-tested-by: Oded Gabbay <[email protected]> Reported-and-tested-by: Chih-Wei Huang <[email protected]> Acked-by: Rik van Riel <[email protected]> Acked-by: Vlastimil Babka <[email protected]> Cc: Daniel Forrest <[email protected]> Cc: Michal Hocko <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Kamal Mostafa <[email protected]> --- mm/mmap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index de25399..d3b8887 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -744,10 +744,12 @@ again: remove_next = 1 + (end > next->vm_end); if (exporter && exporter->anon_vma && !importer->anon_vma) { int error; + importer->anon_vma = exporter->anon_vma; error = anon_vma_clone(importer, exporter); - if (error) + if (error) { + importer->anon_vma = NULL; return error; - importer->anon_vma = exporter->anon_vma; + } } } -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
