From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752679AbdLANSa (ORCPT ); Fri, 1 Dec 2017 08:18:30 -0500 Received: from foss.arm.com ([217.140.101.70]:40708 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752463AbdLANS3 (ORCPT ); Fri, 1 Dec 2017 08:18:29 -0500 Date: Fri, 1 Dec 2017 13:18:32 +0000 From: Will Deacon To: chenjiankang Cc: catalin.marinas@arm.com, linux-kernel@vger.kernel.org, xieyisheng1@huawei.com, wangkefeng.wang@huawei.com Subject: Re: a racy access flag clearing warning when calling mmap system call Message-ID: <20171201131832.GB14823@arm.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 01, 2017 at 03:38:04PM +0800, chenjiankang wrote: > I find a warning by a syzkaller test; > > When the mmap syscall is called to create a virtual memory, > firstly it delete a old huge page mapping area; > Before splitting the huge page, the pmd of a huge page is set up. > But The PTE_AF is zreo belonging to the current pmd of huge page. > I suspect that when the child process is created, the PTE_AF is cleared in copy_one_pte(); > So, the set_pte_at() can have a warning. > > There, whether the set_pte_at() should detect PTE_AF? > > Thanks. > > The log: > > set_pte_at: racy access flag clearing: 00e000009d200bd1 -> 01e000009d200bd1 > ------------[ cut here ]------------ > WARNING: at ../../../../../kernel/linux-4.1/arch/arm64/include/asm/pgtable.h:211 Given that this is a fairly old 4.1 kernel, could you try to reproduce the failure with something more recent, please? We've fixed many bugs since then, some of them involving huge pages. Thanks, Will > Modules linked in: > CPU: 0 PID: 3665 Comm: syz-executor7 Not tainted 4.1.44+ #1 > Hardware name: linux,dummy-virt (DT) > task: ffffffc06a873fc0 ti: ffffffc05aefc000 task.ti: ffffffc05aefc000 > PC is at pmdp_splitting_flush+0x194/0x1b0 > LR is at pmdp_splitting_flush+0x194/0x1b0 > pc : [] lr : [] pstate: 80000145 > sp : ffffffc05aeff770 > x29: ffffffc05aeff770 x28: ffffffc05ae45800 > x27: 0000000020200000 x26: ffffffc061fdf450 > x25: 0000000000020000 x24: 0000000000000001 > x23: ffffffc06333d9c8 x22: ffffffc0014ba000 > x21: 01e000009d200bd1 x20: 00e000009d200bd1 > x19: ffffffc05ae45800 x18: 0000000000000000 > x17: 00000000004b4000 x16: ffffffc00017fdc0 > x15: 00000000038ee280 x14: 3030653130203e2d > x13: 2031646230303264 x12: 3930303030306530 > x11: 30203a676e697261 x10: 656c632067616c66 > x9 : 2073736563636120 x8 : 79636172203a7461 > x7 : ffffffc05aeff430 x6 : ffffffc00015f38c > x5 : 0000000000000003 x4 : 0000000000000000 > x3 : 0000000000000003 x2 : 0000000000010000 > x1 : ffffff9005a03000 x0 : 000000000000004b > Call trace: > [] pmdp_splitting_flush+0x194/0x1b0 > [] split_huge_page_to_list+0x168/0xdb0 > [] __split_huge_page_pmd+0x1b0/0x510 > [] split_huge_page_pmd_mm+0x84/0x88 > [] split_huge_page_address+0xc4/0xe8 > [] __vma_adjust_trans_huge+0x15c/0x190 > [] vma_adjust+0x884/0x9f0 > [] __split_vma.isra.5+0x200/0x310 > [] do_munmap+0x5e0/0x608 > [] mmap_region+0x12c/0x900 > [] do_mmap_pgoff+0x484/0x540 > [] vm_mmap_pgoff+0x128/0x158 > [] SyS_mmap_pgoff+0x188/0x300 > [] sys_mmap+0x58/0x80 >