Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933421AbbDIIyw (ORCPT ); Thu, 9 Apr 2015 04:54:52 -0400 Received: from mail.kernel.org ([198.145.29.136]:42460 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932754AbbDIIyq (ORCPT ); Thu, 9 Apr 2015 04:54:46 -0400 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Konstantin Khlebnikov , Daniel Forrest , Michal Hocko , Linus Torvalds , Zefan Li Subject: [PATCH 3.4 099/176] mm: fix corner case in anon_vma endless growing prevention Date: Thu, 9 Apr 2015 16:45:47 +0800 Message-Id: <1428569224-23820-99-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1428569028-23762-1-git-send-email-lizf@kernel.org> References: <1428569028-23762-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2528 Lines: 71 From: Konstantin Khlebnikov 3.4.107-rc1 review patch. If anyone has any objections, please let me know. ------------------ 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 Reported-and-tested-by: Chris Clayton Reported-and-tested-by: Oded Gabbay Reported-and-tested-by: Chih-Wei Huang Acked-by: Rik van Riel Acked-by: Vlastimil Babka Cc: Daniel Forrest Cc: Michal Hocko Signed-off-by: Linus Torvalds [lizf: Backported to 3.4: define variable @error and return this instead of returning -ENOMEM] Signed-off-by: Zefan Li --- mm/mmap.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index 84dc5fc..f880ca1 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -567,9 +567,14 @@ again: remove_next = 1 + (end > next->vm_end); * shrinking vma had, to cover any anon pages imported. */ if (exporter && exporter->anon_vma && !importer->anon_vma) { - if (anon_vma_clone(importer, exporter)) - return -ENOMEM; + int error; + importer->anon_vma = exporter->anon_vma; + error = anon_vma_clone(importer, exporter); + if (error) { + importer->anon_vma = NULL; + return error; + } } } -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/