Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754937AbbL0Xgi (ORCPT ); Sun, 27 Dec 2015 18:36:38 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35852 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752690AbbL0Xge (ORCPT ); Sun, 27 Dec 2015 18:36:34 -0500 Date: Sun, 27 Dec 2015 18:36:29 -0500 From: Rafael Aquini To: Minchan Kim Cc: Andrew Morton , "Michael S. Tsirkin" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Konstantin Khlebnikov , stable@vger.kernel.org Subject: Re: [PATCH 2/2] virtio_balloon: fix race between migration and ballooning Message-ID: <20151227233629.GC624@t510.redhat.com> References: <1451259313-26353-1-git-send-email-minchan@kernel.org> <1451259313-26353-2-git-send-email-minchan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1451259313-26353-2-git-send-email-minchan@kernel.org> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4020 Lines: 91 On Mon, Dec 28, 2015 at 08:35:13AM +0900, Minchan Kim wrote: > In balloon_page_dequeue, pages_lock should cover the loop > (ie, list_for_each_entry_safe). Otherwise, the cursor page could > be isolated by compaction and then list_del by isolation could > poison the page->lru.{prev,next} so the loop finally could > access wrong address like this. This patch fixes the bug. > > general protection fault: 0000 [#1] SMP > Dumping ftrace buffer: > (ftrace buffer empty) > Modules linked in: > CPU: 2 PID: 82 Comm: vballoon Not tainted 4.4.0-rc5-mm1-access_bit+ #1906 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > task: ffff8800a7ff0000 ti: ffff8800a7fec000 task.ti: ffff8800a7fec000 > RIP: 0010:[] [] balloon_page_dequeue+0x54/0x130 > RSP: 0018:ffff8800a7fefdc0 EFLAGS: 00010246 > RAX: ffff88013fff9a70 RBX: ffffea000056fe00 RCX: 0000000000002b7d > RDX: ffff88013fff9a70 RSI: ffffea000056fe00 RDI: ffff88013fff9a68 > RBP: ffff8800a7fefde8 R08: ffffea000056fda0 R09: 0000000000000000 > R10: ffff8800a7fefd90 R11: 0000000000000001 R12: dead0000000000e0 > R13: ffffea000056fe20 R14: ffff880138809070 R15: ffff880138809060 > FS: 0000000000000000(0000) GS:ffff88013fc40000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > CR2: 00007f229c10e000 CR3: 00000000b8b53000 CR4: 00000000000006a0 > Stack: > 0000000000000100 ffff880138809088 ffff880138809000 ffff880138809060 > 0000000000000046 ffff8800a7fefe28 ffffffff812c86d3 ffff880138809020 > ffff880138809000 fffffffffff91900 0000000000000100 ffff880138809060 > Call Trace: > [] leak_balloon+0x93/0x1a0 > [] balloon+0x217/0x2a0 > [] ? __schedule+0x31e/0x8b0 > [] ? abort_exclusive_wait+0xb0/0xb0 > [] ? update_balloon_stats+0xf0/0xf0 > [] kthread+0xc9/0xe0 > [] ? kthread_park+0x60/0x60 > [] ret_from_fork+0x3f/0x70 > [] ? kthread_park+0x60/0x60 > Code: 8d 60 e0 0f 84 af 00 00 00 48 8b 43 20 a8 01 75 3b 48 89 d8 f0 0f ba 28 00 72 10 48 8b 03 f6 c4 08 75 2f 48 89 df e8 8c 83 f9 ff <49> 8b 44 24 20 4d 8d 6c 24 20 48 83 e8 20 4d 39 f5 74 7a 4c 89 > RIP [] balloon_page_dequeue+0x54/0x130 > RSP > ---[ end trace 43cf28060d708d5f ]--- > Kernel panic - not syncing: Fatal exception > Dumping ftrace buffer: > (ftrace buffer empty) > Kernel Offset: disabled > > Cc: > Signed-off-by: Minchan Kim > --- > mm/balloon_compaction.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c > index d3116be5a00f..300117f1a08f 100644 > --- a/mm/balloon_compaction.c > +++ b/mm/balloon_compaction.c > @@ -61,6 +61,7 @@ struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info) > bool dequeued_page; > > dequeued_page = false; > + spin_lock_irqsave(&b_dev_info->pages_lock, flags); > list_for_each_entry_safe(page, tmp, &b_dev_info->pages, lru) { > /* > * Block others from accessing the 'page' while we get around > @@ -75,15 +76,14 @@ struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info) > continue; > } > #endif > - spin_lock_irqsave(&b_dev_info->pages_lock, flags); > balloon_page_delete(page); > __count_vm_event(BALLOON_DEFLATE); > - spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); > unlock_page(page); > dequeued_page = true; > break; > } > } > + spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); > > if (!dequeued_page) { > /* > -- > 1.9.1 > Acked-by: Rafael Aquini -- 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/