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Fri, 14 Aug 2026 14:41:35 +0000 (GMT) Received: from osiris (unknown [9.111.40.200]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTPS; Fri, 14 Aug 2026 14:41:35 +0000 (GMT) Date: Fri, 14 Aug 2026 16:41:34 +0200 From: Heiko Carstens To: Vasily Gorbik Cc: Mikhail Zaslonko , Alexander Egorenkov , linux-s390@vger.kernel.org Subject: Re: [PATCH 1/2] s390/ipl: Fix NULL deref in kdump without re-IPL parm block Message-ID: <20260814144134.135106Adf-hca@linux.ibm.com> References: Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODE0MDExMSBTYWx0ZWRfX+A4RVnr9YkON T7Ez1GiYUthS2Wo8/fDUDMLoe+MtWB1A91I1IhqYt02eu19wWXHv3lqL/XNaggfUkDp0wuhFVsg pY573efaTMVNuuD5Kbc5ugSt4BO/nJ1vJZGfc9NiE7k9wlI+XhRQNab6pjRzP6KrOefxLMBw5f6 FtcbalyQckBfaGabXIp+k8k5Vse5/IONQKRm2W2o87OGML2JA6mHxfOEab/13wvsGFSJKiX5WEe kgdmI6FkDCgTRBLKJ65nG2ndtWHTf+TtnSSm/EUDAE9pvUhf1PyNKt2RlnJdh4X5KjDI3x4V5w5 LrAVTLB+PY0MmGSbqPrgmDO2bCFTthmL9pW2NN3mr2wMkDc/xG1PsiVq94c3UybZ+w7uwy8wbnm qlfXFcBQBhGFa6oIYzhWcp/xqkSsF6zs4HGISV2CAKTz0QCeRdm4NBd8LvC4AejVgUrqdvRZ1vf ZvxQir2SbG0Nq6kRmeA== X-Proofpoint-ORIG-GUID: 9SNSmtXsYIYhUhiQw1NfORbFjWbHyq4Y X-Proofpoint-Spam-Info: AW1haW4tMjYwODE0MDExMSBTYWx0ZWRfX48FoH2IUAoxs rM/eap7c474UHjYEbhFJh0jpJKlMHBSH3NYqzlK1fG2uTVINpRlZqxEJ5OHRijtt3mXBaGTBz8S LJBj8trusvBu86qnB+Fd4DrjIlAg/n4= X-Authority-Analysis: v=2.4 cv=IfK3n2qa c=1 sm=1 tr=0 ts=6a7f2924 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=kj9zAlcOel0A:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VnNF1IyMAAAA:8 a=wlvK-vJGsJdvzziIeEIA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-GUID: 9SNSmtXsYIYhUhiQw1NfORbFjWbHyq4Y 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=2026-08-14_05,2026-08-12_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 priorityscore=1501 impostorscore=0 bulkscore=0 clxscore=1015 lowpriorityscore=0 adultscore=0 malwarescore=0 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608140111 On Thu, Aug 13, 2026 at 01:06:54PM +0200, Vasily Gorbik wrote: > Some IPL types, like HMC FTP boot or QEMU direct kernel boot, might > not provide an IPL parameter block. In this case, reipl_type_init() > selects IPL_TYPE_UNKNOWN, and reipl_block_actual remains NULL. > > kdump passes the re-IPL parameter block to the dump kernel through > os_info. Before commit 3b9678472bab ("s390/ipl: correct kdump reipl > block checksum calculation"), the os_info entry was added only for > IPL types which initialized reipl_block_actual. That commit moved the > os_info update to machine_crash_shutdown(), making it unconditional. As > a result, set_os_info_reipl_block() dereferences reipl_block_actual for > IPL_TYPE_UNKNOWN. This may happen to work by chance when address zero > contains readable lowcore data and the resulting empty os_info entry is > ignored by the dump kernel. > > Skip the os_info update when no re-IPL parameter block is available. > Kdump then collect the dump and reboot without setting re-IPL parameter > block. > > Fixes: 3b9678472bab ("s390/ipl: correct kdump reipl block checksum calculation") > Signed-off-by: Vasily Gorbik > --- > arch/s390/kernel/ipl.c | 2 ++ > 1 file changed, 2 insertions(+) Reviewed-by: Heiko Carstens