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 Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9BB0CC05027 for ; Thu, 2 Feb 2023 07:01:55 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4P6qTY5F6Cz3f67 for ; Thu, 2 Feb 2023 18:01:53 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=AU8PJPhp; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linux.ibm.com (client-ip=148.163.158.5; helo=mx0a-001b2d01.pphosted.com; envelope-from=hbathini@linux.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=AU8PJPhp; dkim-atps=neutral Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4P6qSS0pztz3cMj for ; Thu, 2 Feb 2023 18:00:55 +1100 (AEDT) Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 3124g5tG004820; Thu, 2 Feb 2023 07:00:48 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=message-id : date : mime-version : subject : to : cc : references : from : in-reply-to : content-type : content-transfer-encoding; s=pp1; bh=c41cUAYAIuungBjJWqHXw8J37UMkxAk/D8iCocBEyDY=; b=AU8PJPhp/lVlmv0YfUCmbQ7VygBF8o05/jjClAC9UVpSskSsXbCPKiCm3QH/IBYTucyF zRURzBjP7/r6K8+kix7BTYhwMtI3kj/VxnMlhV78QDMVB2UvjdhOwvlD/KGO7oNR7t4i WoEW3ujTfNFS4RwdNMrDYf5Jjj2056sgrDFm9tIHhzhqvMEX404WCsa37ruM2gMwld80 lTIQEiDlf92BMU4WVU7vY+mF/RKkb+JlWNRAful77EsR2tgNavyOtLFCxRzE4W06U3qG jx+P3oFKAlv8iE0Q1ygUYpDVaeJrlI4YIh08EHNN8CJdU/ns7o06kUk3alxcy+aZRZ/g HA== Received: from ppma03ams.nl.ibm.com (62.31.33a9.ip4.static.sl-reverse.com [169.51.49.98]) by mx0b-001b2d01.pphosted.com (PPS) with ESMTPS id 3ng5gybfe3-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 02 Feb 2023 07:00:47 +0000 Received: from pps.filterd (ppma03ams.nl.ibm.com [127.0.0.1]) by ppma03ams.nl.ibm.com (8.17.1.19/8.17.1.19) with ESMTP id 311JCYuM012873; Thu, 2 Feb 2023 07:00:45 GMT Received: from smtprelay01.fra02v.mail.ibm.com ([9.218.2.227]) by ppma03ams.nl.ibm.com (PPS) with ESMTPS id 3ncvtydt6k-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 02 Feb 2023 07:00:45 +0000 Received: from smtpav03.fra02v.mail.ibm.com (smtpav03.fra02v.mail.ibm.com [10.20.54.102]) by smtprelay01.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 31270g1N51511794 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 2 Feb 2023 07:00:42 GMT Received: from smtpav03.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 263E32004F; Thu, 2 Feb 2023 07:00:42 +0000 (GMT) Received: from smtpav03.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 51D832004B; Thu, 2 Feb 2023 07:00:41 +0000 (GMT) Received: from [9.43.104.186] (unknown [9.43.104.186]) by smtpav03.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 2 Feb 2023 07:00:41 +0000 (GMT) Message-ID: <2f211d64-cf91-1d3b-fd79-eb827e949caa@linux.ibm.com> Date: Thu, 2 Feb 2023 12:30:40 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [PATCH] powerpc/kexec_file: Fix division by zero in extra size estimation Content-Language: en-US To: Michael Ellerman , linuxppc-dev@lists.ozlabs.org References: <20230130014707.541110-1-mpe@ellerman.id.au> From: Hari Bathini In-Reply-To: <20230130014707.541110-1-mpe@ellerman.id.au> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: ECzjCZuz_WlYmJfyK5V7QYwMCY0xElRP X-Proofpoint-ORIG-GUID: ECzjCZuz_WlYmJfyK5V7QYwMCY0xElRP X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.930,Hydra:6.0.562,FMLib:17.11.122.1 definitions=2023-02-01_15,2023-01-31_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 clxscore=1011 bulkscore=0 suspectscore=0 phishscore=0 adultscore=0 impostorscore=0 spamscore=0 mlxlogscore=999 priorityscore=1501 mlxscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2212070000 definitions=main-2302020061 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: sourabhjain@linux.ibm.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Thanks for the fix, Michael. On 30/01/23 7:17 am, Michael Ellerman wrote: > In kexec_extra_fdt_size_ppc64() there's logic to estimate how much > extra space will be needed in the device tree for some memory related > properties. > > That logic uses the size of RAM divided by drmem_lmb_size() to do the > estimation. However drmem_lmb_size() can be zero if the machine has no > hotpluggable memory configured, which is the case when booting with qemu > and no maxmem=x parameter is passed (the default). > > The division by zero is reported by UBSAN, and can also lead to an > overflow and a warning from kvmalloc, and kdump kernel loading fails: > > WARNING: CPU: 0 PID: 133 at mm/util.c:596 kvmalloc_node+0x15c/0x160 > Modules linked in: > CPU: 0 PID: 133 Comm: kexec Not tainted 6.2.0-rc5-03455-g07358bd97810 #223 > Hardware name: IBM pSeries (emulated by qemu) POWER9 (raw) 0x4e1200 0xf000005 of:SLOF,git-dd0dca pSeries > NIP: c00000000041ff4c LR: c00000000041fe58 CTR: 0000000000000000 > REGS: c0000000096ef750 TRAP: 0700 Not tainted (6.2.0-rc5-03455-g07358bd97810) > MSR: 800000000282b033 CR: 24248242 XER: 2004011e > CFAR: c00000000041fed0 IRQMASK: 0 > ... > NIP kvmalloc_node+0x15c/0x160 > LR kvmalloc_node+0x68/0x160 > Call Trace: > kvmalloc_node+0x68/0x160 (unreliable) > of_kexec_alloc_and_setup_fdt+0xb8/0x7d0 > elf64_load+0x25c/0x4a0 > kexec_image_load_default+0x58/0x80 > sys_kexec_file_load+0x5c0/0x920 > system_call_exception+0x128/0x330 > system_call_vectored_common+0x15c/0x2ec > > To fix it, skip the calculation if drmem_lmb_size() is zero. > > Fixes: 2377c92e37fe ("powerpc/kexec_file: fix FDT size estimation for kdump kernel") > Cc: stable@vger.kernel.org # v5.12+ > Signed-off-by: Michael Ellerman Acked-by: Hari Bathini > --- > arch/powerpc/kexec/file_load_64.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c > index af8854f9eae3..3caee570e79b 100644 > --- a/arch/powerpc/kexec/file_load_64.c > +++ b/arch/powerpc/kexec/file_load_64.c > @@ -989,10 +989,12 @@ unsigned int kexec_extra_fdt_size_ppc64(struct kimage *image) > * linux,drconf-usable-memory properties. Get an approximate on the > * number of usable memory entries and use for FDT size estimation. > */ > - usm_entries = ((memblock_end_of_DRAM() / drmem_lmb_size()) + > - (2 * (resource_size(&crashk_res) / drmem_lmb_size()))); > - > - extra_size = (unsigned int)(usm_entries * sizeof(u64)); > + if (drmem_lmb_size()) { > + usm_entries = ((memblock_end_of_DRAM() / drmem_lmb_size()) + > + (2 * (resource_size(&crashk_res) / drmem_lmb_size()))); > + extra_size = (unsigned int)(usm_entries * sizeof(u64)); > + } else > + extra_size = 0; > > /* > * Get the number of CPU nodes in the current DT. This allows to