Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1032919AbbKEJPi (ORCPT ); Thu, 5 Nov 2015 04:15:38 -0500 Received: from vserver.eikelenboom.it ([84.200.39.61]:35752 "EHLO smtp.eikelenboom.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031070AbbKEJPb (ORCPT ); Thu, 5 Nov 2015 04:15:31 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 05 Nov 2015 10:13:56 +0100 From: Sander Eikelenboom To: Boris Ostrovsky , Stephen Smalley Cc: linux-kernel@vger.kernel.org, x86@kernel.org, David Vrabel , xen-devel@lists.xen.org, mingo.kernel.org@gmail.com Subject: Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with =?UTF-8?Q?CONFIG=5FDEBUG=5FWX=20enabled=3A=20RIP=3A=20ptdump=5Fwalk=5Fpgd?= =?UTF-8?Q?=5Flevel=5Fcore?= In-Reply-To: <563A910F.7060008@oracle.com> References: <9184aedc84bf5274c290183fa60b48e9@eikelenboom.it> <563A29C4.7020400@tycho.nsa.gov> <60febac0220bd2b5df2fd0d86c8d40ae@eikelenboom.it> <563A52CD.5030903@tycho.nsa.gov> <8bbf050578e9254ac3bf1d941dc0fb19@eikelenboom.it> <563A910F.7060008@oracle.com> Message-ID: <80b3ed527b208d28ee05fb627bc28d91@eikelenboom.it> User-Agent: Roundcube Webmail/0.9.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8446 Lines: 204 On 2015-11-05 00:13, Boris Ostrovsky wrote: > On 11/04/2015 03:02 PM, Sander Eikelenboom wrote: >> On 2015-11-04 19:47, Stephen Smalley wrote: >>> On 11/04/2015 01:28 PM, Sander Eikelenboom wrote: >>>> On 2015-11-04 16:52, Stephen Smalley wrote: >>>>> On 11/04/2015 06:55 AM, Sander Eikelenboom wrote: >>>>>> Hi All, >>>>>> >>>>>> I just tried to boot with the current linus mergewindow tree under >>>>>> Xen. >>>>>> It fails with a kernel panic at boot with the new >>>>>> "CONFIG_DEBUG_WX" >>>>>> option enabled. >>>>>> Disabling it makes the kernel boot fine. >>>>>> >>>>>> The splat: >>>>>> [ 18.424241] Freeing unused kernel memory: 1104K >>>>>> (ffffffff822fc000 - >>>>>> ffffffff82410000) >>>>>> [ 18.430314] Write protecting the kernel read-only data: 18432k >>>>>> [ 18.441054] Freeing unused kernel memory: 1144K >>>>>> (ffff880001ae2000 - >>>>>> ffff880001c00000) >>>>>> [ 18.447966] Freeing unused kernel memory: 1560K >>>>>> (ffff88000207a000 - >>>>>> ffff880002200000) >>>>>> [ 18.453947] BUG: unable to handle kernel paging request at >>>>>> ffff88055c883000 >>>>>> [ 18.459943] IP: [] >>>>>> ptdump_walk_pgd_level_core+0x20e/0x440 >>>>>> [ 18.465847] PGD 2212067 PUD 0 >>>>>> [ 18.471564] Oops: 0000 [#1] SMP >>>>>> [ 18.477248] Modules linked in: >>>>>> [ 18.482918] CPU: 2 PID: 1 Comm: swapper/0 Not tainted >>>>>> 4.3.0-mw-20151104-linus-doflr+ #1 >>>>>> [ 18.488804] Hardware name: MSI MS-7640/890FXA-GD70 (MS-7640) , >>>>>> BIOS >>>>>> V1.8B1 09/13/2010 >>>>>> [ 18.494778] task: ffff880059b90000 ti: ffff880059b98000 >>>>>> task.ti: >>>>>> ffff880059b98000 >>>>>> [ 18.500852] RIP: e030:[] [] >>>>>> ptdump_walk_pgd_level_core+0x20e/0x440 >>>>>> [ 18.507102] RSP: e02b:ffff880059b9be48 EFLAGS: 00010296 >>>>>> [ 18.513351] RAX: ffff88055c883000 RBX: ffffffff81ae2000 RCX: >>>>>> ffff880000000000 >>>>>> [ 18.519733] RDX: 0000000000000067 RSI: ffff880059b9be98 RDI: >>>>>> ffff880000001000 >>>>>> [ 18.526129] RBP: ffff880059b9bf00 R08: 0000000000000000 R09: >>>>>> 0000000000000000 >>>>>> [ 18.532522] R10: ffff88005fd0e790 R11: 0000000000000001 R12: >>>>>> ffff880080000000 >>>>>> [ 18.538891] R13: ffffc00000000fff R14: ffff880059b9be98 R15: >>>>>> 0000000000000000 >>>>>> [ 18.545247] FS: 0000000000000000(0000) >>>>>> GS:ffff88005f680000(0000) >>>>>> knlGS:0000000000000000 >>>>>> [ 18.551708] CS: e033 DS: 0000 ES: 0000 CR0: 000000008005003b >>>>>> [ 18.558153] CR2: ffff88055c883000 CR3: 0000000002211000 CR4: >>>>>> 0000000000000660 >>>>>> [ 18.564686] Stack: >>>>>> [ 18.571106] 0000000159b9be50 ffffffff82211000 ffff88055c884000 >>>>>> 0000000000000800 >>>>>> [ 18.577704] 0000800000000000 ffff88055c883000 0000000000000007 >>>>>> ffff88005fd0e790 >>>>>> [ 18.584291] ffff880059b9bed8 ffffffff81156ace 0000000000000001 >>>>>> 0000000000000000 >>>>>> [ 18.590916] Call Trace: >>>>>> [ 18.597458] [] ? >>>>>> free_reserved_area+0x11e/0x120 >>>>>> [ 18.604180] [] >>>>>> ptdump_walk_pgd_level_checkwx+0x12/0x20 >>>>>> [ 18.611014] [] mark_rodata_ro+0xe9/0xf0 >>>>>> [ 18.617819] [] ? rest_init+0x80/0x80 >>>>>> [ 18.624512] [] kernel_init+0x18/0xe0 >>>>>> [ 18.631095] [] ret_from_fork+0x3f/0x70 >>>>>> [ 18.637650] [] ? rest_init+0x80/0x80 >>>>>> [ 18.644178] Code: 70 ff ff ff 48 3b 85 58 ff ff ff 0f 84 c0 fe >>>>>> ff ff >>>>>> 48 8b 85 68 ff ff ff 48 c1 e0 10 48 c1 f8 10 48 89 45 b0 48 8b 85 >>>>>> 70 ff >>>>>> ff ff <48> 8b 38 48 85 ff 0f 85 4e ff ff ff b9 02 00 00 00 31 d2 >>>>>> 4c 89 >>>>>> [ 18.658246] RIP [] >>>>>> ptdump_walk_pgd_level_core+0x20e/0x440 >>>>>> [ 18.665211] RSP >>>>>> [ 18.672073] CR2: ffff88055c883000 >>>>>> [ 18.678852] ---[ end trace d84e34461c40637a ]--- >>>>>> [ 18.685641] Kernel panic - not syncing: Attempted to kill init! >>>>>> exitcode=0x00000009 >>>>>> [ 18.685641] >>>>>> [ 18.699520] Kernel Offset: disable >>>>>> >>>>> >>>>> What's your .config? Does cat /sys/kernel/debug/kernel_page_tables >>>>> produce a similar fault even with CONFIG_DEBUG_WX=n? >>>> >>>> .config is attached >>>> >>>> Hmm that sysfs file doesn't seem to exist then: >>>> # cat /sys/kernel/debug/kernel_page_tables >>>> cat: /sys/kernel/debug/kernel_page_tables: No such file or directory >>> >>> Needs CONFIG_X86_PTDUMP=y. >>> Also assumes you have debugfs mounted there. >> >> Recompiled, and the result is that it also blows up: >> > > Can you try this: > > > diff --git a/arch/x86/mm/dump_pagetables.c > b/arch/x86/mm/dump_pagetables.c > index 1bf417e..b534216 100644 > --- a/arch/x86/mm/dump_pagetables.c > +++ b/arch/x86/mm/dump_pagetables.c > @@ -362,8 +362,13 @@ static void ptdump_walk_pgd_level_core(struct > seq_file *m, pgd_t *pgd, > bool checkwx) > { > #ifdef CONFIG_X86_64 > +/* ffff800000000000 - ffff87ffffffffff is reserved for hypervisor */ > +#define is_hypervisor_range(idx) (paravirt_enabled() && \ > + ((idx >= pgd_index(__PAGE_OFFSET) - 16) && \ > + (idx < pgd_index(__PAGE_OFFSET)))) > pgd_t *start = (pgd_t *) &init_level4_pgt; > #else > +#define is_hypervisor_range(idx) 0 > pgd_t *start = swapper_pg_dir; > #endif > pgprotval_t prot; > @@ -381,7 +386,7 @@ static void ptdump_walk_pgd_level_core(struct > seq_file *m, pgd_t *pgd, > > for (i = 0; i < PTRS_PER_PGD; i++) { > st.current_address = normalize_addr(i * PGD_LEVEL_MULT); > - if (!pgd_none(*start)) { > + if (!pgd_none(*start) && !is_hypervisor_range(i)) { > if (pgd_large(*start) || !pgd_present(*start)) { > prot = pgd_flags(*start); > note_page(m, &st, __pgprot(prot), 1); Hi Boris, Thank for your patch ! It makes "cat /sys/kernel/debug/kernel_page_tables" work and prevents a kernel with CONFIG_DEBUG_WX=y from crashing at boot. It now does give a warning about an insecure W+X mapping, so CONFIG_DEBUG_WX=y seems to be working. No idea how to interpret it though (and if it's a legit warning). -- Sander [ 19.034706] Freeing unused kernel memory: 1104K (ffffffff822fc000 - ffffffff82410000) [ 19.041339] Write protecting the kernel read-only data: 18432k [ 19.052596] Freeing unused kernel memory: 1144K (ffff880001ae2000 - ffff880001c00000) [ 19.060285] Freeing unused kernel memory: 1560K (ffff88000207a000 - ffff880002200000) [ 19.067079] ------------[ cut here ]------------ [ 19.073931] WARNING: CPU: 5 PID: 1 at arch/x86/mm/dump_pagetables.c:225 note_page+0x619/0x7e0() [ 19.081039] x86/mm: Found insecure W+X mapping at address ffff880000000000/0xffff880000000000 [ 19.088293] Modules linked in: [ 19.095477] CPU: 5 PID: 1 Comm: swapper/0 Not tainted 4.3.0-mw-20151104-linus-doflr-withdebugwx-noptdump-ptdumppatch+ #1 [ 19.102971] Hardware name: MSI MS-7640/890FXA-GD70 (MS-7640) , BIOS V1.8B1 09/13/2010 [ 19.110594] ffffffff81f381d3 ffff880059b9bd60 ffffffff81428992 ffff880059b9bda8 [ 19.118239] ffff880059b9bd98 ffffffff810ca7ec ffff8800025d8010 0000000000000004 [ 19.125870] 0010000000000067 ffff880059b9be98 0000000000000000 ffff880059b9bdf8 [ 19.133526] Call Trace: [ 19.141212] [] dump_stack+0x44/0x62 [ 19.148983] [] warn_slowpath_common+0x7c/0xb0 [ 19.156877] [] warn_slowpath_fmt+0x47/0x50 [ 19.164813] [] note_page+0x619/0x7e0 [ 19.172656] [] ptdump_walk_pgd_level_core+0x3b5/0x450 [ 19.180583] [] ptdump_walk_pgd_level_checkwx+0x12/0x20 [ 19.188427] [] mark_rodata_ro+0xe9/0xf0 [ 19.196221] [] ? rest_init+0x80/0x80 [ 19.204012] [] kernel_init+0x18/0xe0 [ 19.211732] [] ret_from_fork+0x3f/0x70 [ 19.219467] [] ? rest_init+0x80/0x80 [ 19.227145] ---[ end trace 5fc0f4297b911570 ]--- [ 19.244382] x86/mm: Checked W+X mappings: FAILED, 4602 W+X pages found. -- 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/