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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A564BC79FB7 for ; Wed, 9 Sep 2026 15:53:35 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A04336B0096; Wed, 9 Sep 2026 11:53:34 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9DBFD6B0098; Wed, 9 Sep 2026 11:53:34 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8F2906B0099; Wed, 9 Sep 2026 11:53:34 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 665A66B0096 for ; Wed, 9 Sep 2026 11:53:34 -0400 (EDT) Received: from smtpin16.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 0A56AC0236 for ; Wed, 9 Sep 2026 15:53:34 +0000 (UTC) X-FDA: 85194668748.16.E108D18 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) by imf09.hostedemail.com (Postfix) with ESMTP id 829FC140008 for ; Wed, 9 Sep 2026 15:53:31 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=FkZShthZ; spf=pass (imf09.hostedemail.com: domain of rnsastry@linux.ibm.com designates 148.163.156.1 as permitted sender) smtp.mailfrom=rnsastry@linux.ibm.com; dmarc=pass (policy=none) header.from=ibm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1788969211; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=9fEv8CVQ+LcrjyrEyKWNY8tE1ZC5nOC4fuPxuTwwtWQ=; b=u/n3z9ywLpx5koq0+a0ieMxXWTI3CtG4rY5itcvb84SaCIC3yPUIgQKeV/ZJYHL9/KGsLo o8vJGKXfKzD7qYpAkVERV+bFskW/bR/teUMpU0Ae0b5hCeM/7GozpzbViWL5iLPX+vkuIp X1hCdcWZw8bssSygC0zlO2/UoovrmqE= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788969211; b=7cEZbiquGxMFCfXnibv2y0Y+5dm8P184EBbjZol4JOy4m2bMVX6n5ZlSxwOifASV2WKk4W yWYUdzu9FHA+Gk4oE9GcJTVJYJizFvH9eTcJLlk88rc1mE6AOXwqX0tXEcvubxPXXK5fbU Co5MvNzK4972y84tKWOoLvdb+vwNN8g= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=FkZShthZ; spf=pass (imf09.hostedemail.com: domain of rnsastry@linux.ibm.com designates 148.163.156.1 as permitted sender) smtp.mailfrom=rnsastry@linux.ibm.com; dmarc=pass (policy=none) header.from=ibm.com Received: from pps.filterd (m0353729.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 689B1hXA1930950; Wed, 9 Sep 2026 15:53:24 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=pp1; bh=9fEv8C VQ+LcrjyrEyKWNY8tE1ZC5nOC4fuPxuTwwtWQ=; b=FkZShthZPf6z6Inxuhf+uF iNXUzguRjPZq6PaXhqShCZ3McDp20T3UU5KU3cjMrWdZqtNCUuSuqfdkm8GvIvLF dd72+XGKDtIjz69shK+IZlKQChWqyKHmF6exXT0UkgZBSqDxfU9Ur7ERBXMUX80P s0bhDfhWZtFY8AxXcf0pCGiGI5KikMBri/OGHlqKcjofQOFEa0vOHAVhylAiOQpt uCOLt6833VHDacYxqLq1mLTEtUp5aex8n856rgslbajZo+ccvWXcR2TgU4TdVmIw 4EHKN7jBzQE3ENXFaCKAqQK2azDDhu9EJCVqra+ip00luEloiWqmnR79lR7H0gcw == Received: from ppma22.wdc07v.mail.ibm.com (5c.69.3da9.ip4.static.sl-reverse.com [169.61.105.92]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 4ggbqk6vp0-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 09 Sep 2026 15:53:23 +0000 (GMT) Received: from pps.filterd (ppma22.wdc07v.mail.ibm.com [127.0.0.1]) by ppma22.wdc07v.mail.ibm.com (8.18.1.7/8.18.1.7) with ESMTP id 689FfE6N015367; Wed, 9 Sep 2026 15:53:22 GMT Received: from smtprelay05.fra02v.mail.ibm.com ([9.218.2.225]) by ppma22.wdc07v.mail.ibm.com (PPS) with ESMTPS id 4ggwswb807-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 09 Sep 2026 15:53:22 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (smtpav01.fra02v.mail.ibm.com [10.20.54.100]) by smtprelay05.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 689FrJXq50987368 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 9 Sep 2026 15:53:20 GMT Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D9F5A2004B; Wed, 9 Sep 2026 15:53:19 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4CF0E20043; Wed, 9 Sep 2026 15:53:10 +0000 (GMT) Received: from [9.61.255.18] (unknown [9.61.255.18]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTPS; Wed, 9 Sep 2026 15:53:09 +0000 (GMT) Message-ID: <30360c50-0238-40e8-b598-bdfda1141cc8@linux.ibm.com> Date: Wed, 9 Sep 2026 21:23:06 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 02/22] coredump: refuse negative skips To: Christian Brauner , linux-fsdevel@vger.kernel.org Cc: Jacob Lalonde , Josef Bacik , Jann Horn , Alexander Viro , Jan Kara , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Omar Sandoval , Jacob Lalonde , Shuah Khan , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linuxppc-dev@lists.ozlabs.org References: <20260820-work-coredump-sparse-v2-0-ba32dd718c51@kernel.org> <20260820-work-coredump-sparse-v2-2-ba32dd718c51@kernel.org> Content-Language: en-US From: R Nageswara Sastry In-Reply-To: <20260820-work-coredump-sparse-v2-2-ba32dd718c51@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: pYL1X5j4L64D3lhY8GC7_PxezJajFPeA X-Proofpoint-Spam-Info: AW1haW4tMjYwOTA5MDE3MyBTYWx0ZWRfXyZQ2yeCYTZ8Y 0zY5ztZt9jhIlCwPuIHMWYJZeFMN1RfSvZmQxlYKHYhZCliMI/1/l/3Wg0EpWXDDd6lWozX46Rp BOsUhsvxP3K7Gf6k9YxbUWZBPcLY48o= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTA5MDE3MyBTYWx0ZWRfX5MyolTbYyMTx 81rdDfK4pUyI4nx4v6Y9Tq/r/gVfH0lueULm43ZNa2On7UJUzNwVwdVblnzuc6TdwypX9OVkabd mY7Y+a3Um2ewoWxHnuzkeZMU9B9ZEx8zXreAkdyeB0s9N4qbY4sE3Mi+N9nw47/d2BRpkyMNGvD 3NamjGc8COyszi5eNpC2WHmCm6ZnIaCNR9nVGU8PKzrDMBSZz7UZmsQZ2GC97VMvBlLdIC1rSRX cnRoYJFT+Rf7HW7PJ/28KPLDCHwRT7HIo66pa7r9Oacak+UAvogwSvhdsx8cRtWmtDzjGv5q3Tx MRgAeULZKoh4YyzTCo7msiB5MQSn0j7ly8YqteQYeKytKoC6USiarP/25m9uwlz0MZyki4TDtFE 9HQGoeP/j1znxi3DPlsn/xA5Dz4ToJDJEyWtDxCPse+ktxUKAo6Dlm+UeqHdrTyl+tA5+qewgyB 79OOPB5Pjo8vswDjYfA== X-Authority-Analysis: v=2.4 cv=JaKMa0KV c=1 sm=1 tr=0 ts=6aa180f3 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=0fa85O3lyfMzuANSHggA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: x7FvKhawyt97Kk1EQB6_XHSAe9xWv9Jr X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-08_03,2026-09-09_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 phishscore=0 impostorscore=0 lowpriorityscore=0 adultscore=0 bulkscore=0 priorityscore=1501 suspectscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2609090173 X-Stat-Signature: m1jaqz8rff1z57qpuur3uehxmu4b1d49 X-Rspam-User: X-Rspamd-Queue-Id: 829FC140008 X-Rspamd-Server: rspam03 X-HE-Tag: 1788969211-685862 X-HE-Meta: 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 2UtmROG4 MO1vn4ej4MWhigd3VRe9ziQ9q2LFJGfbWJsBtcU2aAh4TRkXqDVwjE3VcGv8m3KqoEI3GGGwb4x6CuaV74/RDjKRbuEC3p4F1v8iwNUQl7F5uS000j1ANBuGjh4bLlxv+GpxQh8zMWwlQO1Q9EGuvO1tBSKA/9acEGvMiRBG7pplVtoWIAxnLidM1+7ZHgoA2tygElbai1KCv2PjNLezykjIezJzdAXevo/aPOAm865U5KJpM5B/PEk3pNNMHD3EOacXeyWiw9bB5DK/qWEEf2X3F0Q== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 20.08.2026 4:39 AM, Christian Brauner wrote: > The dump_skip_to() helper calculates a relative skip based on the > absolute positon of the coredump: > > cprm->to_skip = pos - cprm->pos; > > That's easy to mess up for callers and one already did. This risk > endless zero PAGE_SIZE loops or overwriting already written coredump > data thereby corrupting the dump. > > I don't think skipping backwards has any meaning. So warn and refuse. > > Signed-off-by: Christian Brauner (Amutable) Tested-by: R Nageswara Sastry System: ppc64le LPAR (IBM POWER), Linux 7.3-rc2 > --- > fs/coredump.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/fs/coredump.c b/fs/coredump.c > index e68a76ff92a3..ac4e922c9cb9 100644 > --- a/fs/coredump.c > +++ b/fs/coredump.c > @@ -1261,6 +1261,8 @@ EXPORT_SYMBOL(dump_emit); > > void dump_skip_to(struct coredump_params *cprm, unsigned long pos) > { > + if (WARN_ON_ONCE(pos < cprm->pos)) > + return; > cprm->to_skip = pos - cprm->pos; > } > EXPORT_SYMBOL(dump_skip_to); > -- Thanks and Regards R.Nageswara Sastry