Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750824AbaBZHPK (ORCPT ); Wed, 26 Feb 2014 02:15:10 -0500 Received: from mail-vc0-f181.google.com ([209.85.220.181]:62851 "EHLO mail-vc0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750717AbaBZHPI (ORCPT ); Wed, 26 Feb 2014 02:15:08 -0500 MIME-Version: 1.0 In-Reply-To: <530CEFE2.9090909@oracle.com> References: <530CEFE2.9090909@oracle.com> Date: Wed, 26 Feb 2014 15:15:07 +0800 Message-ID: Subject: Re: mm: NULL ptr deref in balance_dirty_pages_ratelimited From: Bob Liu To: Sasha Levin Cc: "linux-mm@kvack.org" , Andrew Morton , LKML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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/