From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f175.google.com (mail-lb0-f175.google.com [209.85.217.175]) by kanga.kvack.org (Postfix) with ESMTP id E34AF6B0032 for ; Tue, 13 Jan 2015 01:53:43 -0500 (EST) Received: by mail-lb0-f175.google.com with SMTP id z11so1027833lbi.6 for ; Mon, 12 Jan 2015 22:53:43 -0800 (PST) Received: from mail-lb0-x229.google.com (mail-lb0-x229.google.com. [2a00:1450:4010:c04::229]) by mx.google.com with ESMTPS id zy1si5890320lbb.12.2015.01.12.22.53.42 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 12 Jan 2015 22:53:42 -0800 (PST) Received: by mail-lb0-f169.google.com with SMTP id p9so1049514lbv.0 for ; Mon, 12 Jan 2015 22:53:42 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20150112122138.f173c6279af0b49565e956d3@linux-foundation.org> References: <20150111135406.13266.42007.stgit@zurg> <20150112122138.f173c6279af0b49565e956d3@linux-foundation.org> Date: Tue, 13 Jan 2015 10:53:42 +0400 Message-ID: Subject: Re: [PATCH] mm: fix corner case in anon_vma endless growing prevention From: Konstantin Khlebnikov Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: "linux-mm@kvack.org" , Linus Torvalds , Linux Kernel Mailing List , Rik van Riel , "Elifaz, Dana" , "Bridgman, John" , Daniel Forrest , Chris Clayton , Oded Gabbay , Michal Hocko , Greg KH On Mon, Jan 12, 2015 at 11:21 PM, Andrew Morton wrote: > On Sun, 11 Jan 2015 16:54:06 +0300 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") > > I've asked Greg not to take 7a3ef208e662 into -stable because of this > problem. So if you still think we should fix this in -stable, could > you please prepare an updated patch and send it to Greg? Will do. But let's wait for some just to be sure that is the last bug here. > >> Tested-by: Chris Clayton >> Tested-by: Oded Gabbay >> Cc: Daniel Forrest >> Cc: Michal Hocko >> Cc: Rik van Riel -- 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