From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 42A09C33CB6 for ; Wed, 22 Jan 2020 15:21:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 226AE2071E for ; Wed, 22 Jan 2020 15:21:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725972AbgAVPVl (ORCPT ); Wed, 22 Jan 2020 10:21:41 -0500 Received: from mx2.suse.de ([195.135.220.15]:48204 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725802AbgAVPVl (ORCPT ); Wed, 22 Jan 2020 10:21:41 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 047F3ACC2; Wed, 22 Jan 2020 15:21:38 +0000 (UTC) Date: Wed, 22 Jan 2020 16:21:36 +0100 From: Michal =?iso-8859-1?Q?Such=E1nek?= To: Libor Pechacek Cc: linuxppc-dev@lists.ozlabs.org, Nathan Fontenot , Nathan Lynch , David Hildenbrand , stable@vger.kernel.org, linux-kernel@vger.kernel.org, Paul Mackerras , Leonardo Bras , Thomas Gleixner , Allison Randal Subject: Re: [PATCH] powerpc: drmem: avoid NULL pointer dereference when drmem is unavailable Message-ID: <20200122152136.GL4113@kitsune.suse.cz> References: <20200116102758.GC25138@fm.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200116102758.GC25138@fm.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 16, 2020 at 11:27:58AM +0100, Libor Pechacek wrote: > In KVM guests drmem structure is only zero initialized. Trying to > manipulate DLPAR parameters results in a crash in this environment. > > $ echo "memory add count 1" > /sys/kernel/dlpar > Oops: Kernel access of bad area, sig: 11 [#1] > LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries > Modules linked in: af_packet(E) rfkill(E) nvram(E) vmx_crypto(E) > gf128mul(E) e1000(E) virtio_balloon(E) rtc_generic(E) crct10dif_vpmsum(E) > btrfs(E) blake2b_generic(E) libcrc32c(E) xor(E) raid6_pq(E) virtio_rng(E) > virtio_blk(E) ohci_pci(E) ehci_pci(E) ohci_hcd(E) ehci_hcd(E) > crc32c_vpmsum(E) usbcore(E) virtio_pci(E) virtio_ring(E) virtio(E) sg(E) > dm_multipath(E) dm_mod(E) scsi_dh_rdac(E) scsi_dh_emc(E) scsi_dh_alua(E) > scsi_mod(E) > CPU: 1 PID: 4114 Comm: bash Kdump: loaded Tainted: G E 5.5.0-rc6-2-default #1 > NIP: c0000000000ff294 LR: c0000000000ff248 CTR: 0000000000000000 > REGS: c0000000fb9d3880 TRAP: 0300 Tainted: G E (5.5.0-rc6-2-default) > MSR: 8000000000009033 CR: 28242428 XER: 20000000 > CFAR: c0000000009a6c10 DAR: 0000000000000010 DSISR: 40000000 IRQMASK: 0 > GPR00: c0000000000ff248 c0000000fb9d3b10 c000000001682e00 0000000000000033 > GPR04: c0000000ff30bf90 c0000000ff394800 0000000000005110 ffffffffffffffe8 > GPR08: 0000000000000000 0000000000000000 00000000fe1c0000 0000000000000000 > GPR12: 0000000000002200 c00000003fffee00 0000000000000000 000000011cbc37c0 > GPR16: 000000011cb27ed0 0000000000000000 000000011cb6dd10 0000000000000000 > GPR20: 000000011cb7db28 000001003ce035f0 000000011cbc7828 000000011cbc6c70 > GPR24: 000001003cf01210 0000000000000000 c0000000ffade4e0 c000000002d7216b > GPR28: 0000000000000001 c000000002d78560 0000000000000000 c0000000015458d0 > NIP [c0000000000ff294] dlpar_memory+0x6e4/0xd00 > LR [c0000000000ff248] dlpar_memory+0x698/0xd00 > Call Trace: > [c0000000fb9d3b10] [c0000000000ff248] dlpar_memory+0x698/0xd00 (unreliable) > [c0000000fb9d3ba0] [c0000000000f5990] handle_dlpar_errorlog+0xc0/0x190 > [c0000000fb9d3c10] [c0000000000f5c58] dlpar_store+0x198/0x4a0 > [c0000000fb9d3cd0] [c000000000c4cb00] kobj_attr_store+0x30/0x50 > [c0000000fb9d3cf0] [c0000000005a37b4] sysfs_kf_write+0x64/0x90 > [c0000000fb9d3d10] [c0000000005a2c90] kernfs_fop_write+0x1b0/0x290 > [c0000000fb9d3d60] [c0000000004a2bec] __vfs_write+0x3c/0x70 > [c0000000fb9d3d80] [c0000000004a6560] vfs_write+0xd0/0x260 > [c0000000fb9d3dd0] [c0000000004a69ac] ksys_write+0xdc/0x130 > [c0000000fb9d3e20] [c00000000000b478] system_call+0x5c/0x68 > Instruction dump: > ebc90000 1ce70018 38e7ffe8 7cfe3a14 7fbe3840 419dff14 fb610068 7fc9f378 > 39000000 4800000c 60000000 4195fef4 <81490010> 39290018 38c80001 7ea93840 > ---[ end trace cc2dd8152608c295 ]--- > > Taking closer look at the code, I can see that for_each_drmem_lmb is a > macro expanding into `for (lmb = &drmem_info->lmbs[0]; lmb <= > &drmem_info->lmbs[drmem_info->n_lmbs - 1]; lmb++)`. When drmem_info->lmbs > is NULL, the loop would iterate through the whole address range if it > weren't stopped by the NULL pointer dereference on the next line. > > This patch aligns for_each_drmem_lmb and for_each_drmem_lmb_in_range macro > behavior with the common C semantics, where the end marker does not belong > to the scanned range, and alters get_lmb_range() semantics. As a side > effect, the wraparound observed in the crash is prevented. > > Fixes: 6c6ea53725b3 ("powerpc/mm: Separate ibm, dynamic-memory data from DT format") > Cc: Michal Suchanek > Cc: stable@vger.kernel.org > Signed-off-by: Libor Pechacek Reviewed-by: Michal Suchanek > --- > arch/powerpc/include/asm/drmem.h | 4 ++-- > arch/powerpc/platforms/pseries/hotplug-memory.c | 4 ++-- > 2 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/arch/powerpc/include/asm/drmem.h b/arch/powerpc/include/asm/drmem.h > index 3d76e1c388c2..28c3d936fdf3 100644 > --- a/arch/powerpc/include/asm/drmem.h > +++ b/arch/powerpc/include/asm/drmem.h > @@ -27,12 +27,12 @@ struct drmem_lmb_info { > extern struct drmem_lmb_info *drmem_info; > > #define for_each_drmem_lmb_in_range(lmb, start, end) \ > - for ((lmb) = (start); (lmb) <= (end); (lmb)++) > + for ((lmb) = (start); (lmb) < (end); (lmb)++) > > #define for_each_drmem_lmb(lmb) \ > for_each_drmem_lmb_in_range((lmb), \ > &drmem_info->lmbs[0], \ > - &drmem_info->lmbs[drmem_info->n_lmbs - 1]) > + &drmem_info->lmbs[drmem_info->n_lmbs]) > > /* > * The of_drconf_cell_v1 struct defines the layout of the LMB data > diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c > index c126b94d1943..4ea6af002e27 100644 > --- a/arch/powerpc/platforms/pseries/hotplug-memory.c > +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c > @@ -236,9 +236,9 @@ static int get_lmb_range(u32 drc_index, int n_lmbs, > if (!start) > return -EINVAL; > > - end = &start[n_lmbs - 1]; > + end = &start[n_lmbs]; > > - last_lmb = &drmem_info->lmbs[drmem_info->n_lmbs - 1]; > + last_lmb = &drmem_info->lmbs[drmem_info->n_lmbs]; > if (end > last_lmb) > return -EINVAL; > > -- > 2.24.1 > > > -- > Libor Pechacek > SUSE Labs Remember to have fun...