From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936990AbcLVJPZ (ORCPT ); Thu, 22 Dec 2016 04:15:25 -0500 Received: from mx2.suse.de ([195.135.220.15]:55514 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761810AbcLVJPX (ORCPT ); Thu, 22 Dec 2016 04:15:23 -0500 Date: Thu, 22 Dec 2016 10:15:20 +0100 From: Michal Hocko To: Wei Yang Cc: trivial@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] mm/memblock.c: check return value of memblock_reserve() in memblock_virt_alloc_internal() Message-ID: <20161222091519.GC6048@dhcp22.suse.cz> References: <1482363033-24754-1-git-send-email-richard.weiyang@gmail.com> <1482363033-24754-3-git-send-email-richard.weiyang@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1482363033-24754-3-git-send-email-richard.weiyang@gmail.com> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 21-12-16 23:30:33, Wei Yang wrote: > memblock_reserve() would add a new range to memblock.reserved in case the > new range is not totally covered by any of the current memblock.reserved > range. If the memblock.reserved is full and can't resize, > memblock_reserve() would fail. > > This doesn't happen in real world now, I observed this during code review. > While theoretically, it has the chance to happen. And if it happens, others > would think this range of memory is still available and may corrupt the > memory. OK, this explains it much better than the previous version! The silent memory corruption is indeed too hard to debug to have this open even when the issue is theoretical. > This patch checks the return value and goto "done" after it succeeds. > > Signed-off-by: Wei Yang Acked-by: Michal Hocko Thanks! > --- > mm/memblock.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/mm/memblock.c b/mm/memblock.c > index 4929e06..d0f2c96 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > @@ -1274,18 +1274,17 @@ static void * __init memblock_virt_alloc_internal( > > if (max_addr > memblock.current_limit) > max_addr = memblock.current_limit; > - > again: > alloc = memblock_find_in_range_node(size, align, min_addr, max_addr, > nid, flags); > - if (alloc) > + if (alloc && !memblock_reserve(alloc, size)) > goto done; > > if (nid != NUMA_NO_NODE) { > alloc = memblock_find_in_range_node(size, align, min_addr, > max_addr, NUMA_NO_NODE, > flags); > - if (alloc) > + if (alloc && !memblock_reserve(alloc, size)) > goto done; > } > > @@ -1303,7 +1302,6 @@ static void * __init memblock_virt_alloc_internal( > > return NULL; > done: > - memblock_reserve(alloc, size); > ptr = phys_to_virt(alloc); > memset(ptr, 0, size); > > -- > 2.5.0 -- Michal Hocko SUSE Labs