Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2993440AbbEPI3n (ORCPT ); Sat, 16 May 2015 04:29:43 -0400 Received: from bband-dyn183.178-41-215.t-com.sk ([178.41.215.183]:22842 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1030344AbbEPIQ6 (ORCPT ); Sat, 16 May 2015 04:16:58 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Konstantin Khlebnikov , Daniel Forrest , Michal Hocko , Linus Torvalds , Jiri Slaby Subject: [PATCH 3.12 110/142] mm: fix corner case in anon_vma endless growing prevention Date: Sat, 16 May 2015 09:37:50 +0200 Message-Id: <4cd01168571b39f9e5bbdab6e43b88757df61067.1431761807.git.jslaby@suse.cz> X-Mailer: git-send-email 2.3.7 In-Reply-To: <70c3d4ae1322b9e9bd7443ef574af5635234a0fa.1431761807.git.jslaby@suse.cz> References: <70c3d4ae1322b9e9bd7443ef574af5635234a0fa.1431761807.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2431 Lines: 67 From: Konstantin Khlebnikov 3.12-stable 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 Cc: stable@vger.kernel.org # to match back-porting of 7a3ef208e662 Signed-off-by: Linus Torvalds Signed-off-by: Jiri Slaby --- mm/mmap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index c3ed083cfb59..0ace27f78982 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -748,10 +748,12 @@ 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; + } } } -- 2.3.7 -- 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/