Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751484AbaBZOJ7 (ORCPT ); Wed, 26 Feb 2014 09:09:59 -0500 Received: from mta-out.inet.fi ([195.156.147.13]:53924 "EHLO jenni2.inet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750811AbaBZOJ5 (ORCPT ); Wed, 26 Feb 2014 09:09:57 -0500 Date: Wed, 26 Feb 2014 16:09:41 +0200 From: "Kirill A. Shutemov" To: Bob Liu Cc: Sasha Levin , "linux-mm@kvack.org" , Andrew Morton , LKML Subject: Re: mm: NULL ptr deref in balance_dirty_pages_ratelimited Message-ID: <20140226140941.GA31230@node.dhcp.inet.fi> References: <530CEFE2.9090909@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.22.1-rc1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 26, 2014 at 03:15:07PM +0800, Bob Liu wrote: > On Wed, Feb 26, 2014 at 3:32 AM, Sasha Levin wrote: > > Hi all, > > > > While fuzzing with trinity inside a KVM tools running latest -next kernel > > I've stumbled on the following spew: > > > > [ 232.869443] BUG: unable to handle kernel NULL pointer dereference at > > 0000000000000020 > > [ 232.870230] IP: [] > > balance_dirty_pages_ratelimited+0x1e/0x150 > > [ 232.870230] PGD 586e1d067 PUD 586e1e067 PMD 0 > > [ 232.870230] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC > > [ 232.870230] Dumping ftrace buffer: > > [ 232.870230] (ftrace buffer empty) > > [ 232.870230] Modules linked in: > > [ 232.870230] CPU: 36 PID: 9707 Comm: trinity-c36 Tainted: G W > > 3.14.0-rc4-next-20140225-sasha-00010-ga117461 #42 > > [ 232.870230] task: ffff880586dfb000 ti: ffff880586e34000 task.ti: > > ffff880586e34000 > > [ 232.870230] RIP: 0010:[] > > [] balance_dirty_pages_ratelimited+0x1e/0x150 > > [ 232.870230] RSP: 0000:ffff880586e35c58 EFLAGS: 00010282 > > [ 232.870230] RAX: 0000000000000000 RBX: ffff880582831361 RCX: > > 0000000000000007 > > [ 232.870230] RDX: 0000000000000007 RSI: ffff880586dfbcc0 RDI: > > ffff880582831361 > > [ 232.870230] RBP: ffff880586e35c78 R08: 0000000000000000 R09: > > 0000000000000000 > > [ 232.870230] R10: 0000000000000001 R11: 0000000000000001 R12: > > 00007f58007ee000 > > [ 232.870230] R13: ffff880c8d6d4f70 R14: 0000000000000200 R15: > > ffff880c8dcce710 > > [ 232.870230] FS: 00007f58018bb700(0000) GS:ffff880c8e800000(0000) > > knlGS:0000000000000000 > > [ 232.870230] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > > [ 232.870230] CR2: 0000000000000020 CR3: 0000000586e1c000 CR4: > > 00000000000006e0 > > [ 232.870230] Stack: > > [ 232.870230] ffff880586e35c78 ffff880586e33400 00007f58007ee000 > > ffff880c8d6d4f70 > > [ 232.870230] ffff880586e35cd8 ffffffff8127d241 0000000000000001 > > 0000000000000001 > > [ 232.870230] 0000000000000000 ffffea0032337080 0000000080000000 > > ffff880586e33400 > > [ 232.870230] Call Trace: > > [ 232.870230] [] do_shared_fault+0x1a1/0x1f0 > > [ 232.870230] [] handle_pte_fault+0xc8/0x230 > > [ 232.870230] [] ? delay_tsc+0xea/0x110 > > [ 232.870230] [] __handle_mm_fault+0x36e/0x3a0 > > [ 232.870230] [] ? rcu_read_unlock+0x5d/0x60 > > [ 232.870230] [] > > handle_mm_fault+0x10b/0x1b0 > > [ 232.870230] [] ? __do_page_fault+0x2e2/0x590 > > [ 232.870230] [] __do_page_fault+0x551/0x590 > > [ 232.870230] [] ? > > vtime_account_user+0x91/0xa0 > > [ 232.870230] [] ? > > context_tracking_user_exit+0xa8/0x1c0 > > [ 232.870230] [] ? > > _raw_spin_unlock+0x30/0x50 > > [ 232.870230] [] ? > > vtime_account_user+0x91/0xa0 > > [ 232.870230] [] ? > > context_tracking_user_exit+0xa8/0x1c0 > > [ 232.870230] [] do_page_fault+0x3d/0x70 > > [ 232.870230] [] do_async_page_fault+0x35/0x100 > > [ 232.870230] [] > > async_page_fault+0x28/0x30 > > [ 232.870230] Code: 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 48 > > 83 ec 20 48 89 5d e8 4c 89 65 f0 4c 89 6d f8 48 89 fb 48 8b 87 50 01 00 00 > > 40 20 01 0f 85 18 01 00 00 65 48 8b 14 25 40 da 00 00 44 8b > > [ 232.870230] RIP [] > > balance_dirty_pages_ratelimited+0x1e/0x150 > > [ 232.870230] RSP > > [ 232.870230] CR2: 0000000000000020 > > > > > > Could you please test below patch? I think it may fix this issue. What stops compiler from transform this back to unpatched? Do you relay on unlock_page() to have a compiler barrier? > > diff --git a/mm/memory.c b/mm/memory.c > index 548d97e..90cea22 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -3419,6 +3419,7 @@ static int do_shared_fault(struct mm_struct *mm, > struct vm_area_struct *vma, > pgoff_t pgoff, unsigned int flags, pte_t orig_pte) > { > struct page *fault_page; > + struct address_space *mapping; > spinlock_t *ptl; > pte_t *pte; > int dirtied = 0; > @@ -3454,13 +3455,14 @@ static int do_shared_fault(struct mm_struct > *mm, struct vm_area_struct *vma, > > if (set_page_dirty(fault_page)) > dirtied = 1; > + mapping = fault_page->mapping; > unlock_page(fault_page); > - if ((dirtied || vma->vm_ops->page_mkwrite) && fault_page->mapping) { > + if ((dirtied || vma->vm_ops->page_mkwrite) && mapping) { > /* > * Some device drivers do not set page.mapping but still > * dirty their pages > */ > - balance_dirty_pages_ratelimited(fault_page->mapping); > + balance_dirty_pages_ratelimited(mapping); > } > > /* file_update_time outside page_lock */ > -- > 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/ -- Kirill A. Shutemov -- 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/