From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f43.google.com (mail-wg0-f43.google.com [74.125.82.43]) by kanga.kvack.org (Postfix) with ESMTP id 66D136B009C for ; Sun, 11 Jan 2015 09:25:25 -0500 (EST) Received: by mail-wg0-f43.google.com with SMTP id k14so15322530wgh.2 for ; Sun, 11 Jan 2015 06:25:24 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id z2si8681212wib.91.2015.01.11.06.25.23 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 11 Jan 2015 06:25:24 -0800 (PST) Message-ID: <54B287BE.3010107@redhat.com> Date: Sun, 11 Jan 2015 09:25:02 -0500 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH] mm: fix corner case in anon_vma endless growing prevention References: <20150111135406.13266.42007.stgit@zurg> In-Reply-To: <20150111135406.13266.42007.stgit@zurg> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Konstantin Khlebnikov , linux-mm@kvack.org, Andrew Morton , Linus Torvalds , linux-kernel@vger.kernel.org Cc: "Elifaz, Dana" , "Bridgman, John" , Daniel Forrest , Chris Clayton , Oded Gabbay , Michal Hocko -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 01/11/2015 08:54 AM, Konstantin Khlebnikov wrote: > Fix for BUG_ON(anon_vma->degree) splashes in unlink_anon_vmas() > ("kernel BUG at mm/rmap.c:399!"). > > 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 Fixes: > 7a3ef208e662 ("mm: prevent endless growth of anon_vma hierarchy") > Tested-by: Chris Clayton Tested-by: Oded > Gabbay Cc: Daniel Forrest > Cc: Michal Hocko Cc: > Rik van Riel Acked-by: Rik van Riel - -- All rights reversed -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJUsoe+AAoJEM553pKExN6D4x0H/RpBJella2+JhOBPyCBtLY7Z 9w8n14TlqEq7cK/WRmjhYZfVMNGIG3MDe+nAH0hTF0teh/MvJuAkraYnPxtIZYqX R7IpNOUS3HJBLqsRjNdVNsoMnWOGBC6j/RV70pLj1VklZnq/VDsUPybm0XWk1oh6 nC1QhdLfcnuaFS4M1lzsSyURwQYxi+2vv/kFdtYscArTYmjI7I4gCP3fD7lQKCwK za0z/oZb5Z5cOHXyQfe/HUROCCNUZUQfcX1XvW+TWvuwcatOvKeVCmJAy5/aPkfH THtwAP6EyZpu5XwsYXCNfbyalqYpH5lKxd5C+vG86YKEYZyeqRLKLeYAVY3yTho= =v95A -----END PGP SIGNATURE----- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org