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Thu, 13 Aug 2026 13:57:08 +0000 (GMT) Received: from [9.224.77.77] (unknown [9.224.77.77]) by smtpav06.wdc07v.mail.ibm.com (Postfix) with ESMTPS; Thu, 13 Aug 2026 13:57:08 +0000 (GMT) Message-ID: <7faf2317-1e49-4e99-a816-900cecc02e92@linux.ibm.com> Date: Thu, 13 Aug 2026 15:57:05 +0200 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] s390/ipl: Fix NULL deref in dump_reipl without re-IPL parm block To: Vasily Gorbik , Alexander Egorenkov , Heiko Carstens Cc: linux-s390@vger.kernel.org References: Content-Language: en-US From: Mikhail Zaslonko In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 47myq0YW1C_D1i2w9HrZT7eu_PMn8H7g X-Authority-Analysis: v=2.4 cv=PbDPQChd c=1 sm=1 tr=0 ts=6a7dcd38 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=p1M8u0mKESfYOS3vc_EA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODEzMDA5NiBTYWx0ZWRfX4rQ3KVk0upfu eaoWYs1hcPzPUgel7ftxZ23XXW2FE5v/s5BCDbeBTTmLgIdOPo34Ol9Z/IBZRBPVyGJawHS7+Ox nCCQJ4+5SvlRYmcTpExEHMGz5MqZt3DHwNEh7uywnJHR2qhCUVYyto7X4dmp4FE27eOq6lPS5mC MM3Lqj0m118J+l3DPqNK0Aa9/konc1eYqoDtKFFATyhbsDjXkA0DOVaoT8lRNwQl+d438koA316 Zcfj/Sv8QTRFB5ZKB4ZfHX+oY+6UCnbl5WrGU3pieStu6jrhz8gMqg1pOg1GXFLrQi97cQmDn9J JC9AE+dmON0W2COeT7GjoSlLUB2lhNQOCo56g0KO19CeuXnKMJPoX8cEoXyMzxT9fJxWJtk8N4k 9QO4KKqQrvziavzQ6NJw7NWYbbb57zbN0rXa9ImQesxia1vCdAKtjaKoRJkoVLO+LeH9CbOMMZx gwGUabdsqnbUJx0pvLQ== X-Proofpoint-ORIG-GUID: 47myq0YW1C_D1i2w9HrZT7eu_PMn8H7g X-Proofpoint-Spam-Info: AW1haW4tMjYwODEzMDA5NiBTYWx0ZWRfX5h8IgQrJArk5 RJTZpVAiuzYzJ1boYLae3bYu6PtT2+VX7M2qN2gNZc0GtSTcjJEMsIGN/hMyqoQmZ/u5RMdWE3b 7bwg95FCsY6zCVc8Aji3qe4kisT9vs0= 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=2026-08-13_04,2026-08-12_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 bulkscore=0 impostorscore=0 malwarescore=0 adultscore=0 clxscore=1011 priorityscore=1501 suspectscore=0 phishscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608130096 On 13-Aug-26 13:06, Vasily Gorbik wrote: > Unlike kdump, which passes the re-IPL parameter block through os_info, > the stand-alone dump passes it through the IPL parm block address and > checksum in lowcore. > > 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. Nevertheless, > dump_reipl_run() unconditionally dereferences it when preparing the > lowcore fields. This may happen to work by chance when address zero > contains readable lowcore data. A zero IPL parameter block address is > then stored in lowcore, causing the stand-alone dumper to enter disabled > wait after completing the dump. > > Explicitly store a zero IPL parameter block address and checksum when no > re-IPL parameter block is available. This does not change the behavior: > the stand-alone dumper completes the dump and halts, while valid re-IPL > parameter blocks continue to be handled as before. > > Fixes: 099b76513992 ("[S390] Automatic IPL after dump") > Signed-off-by: Vasily Gorbik > --- > arch/s390/kernel/ipl.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/arch/s390/kernel/ipl.c b/arch/s390/kernel/ipl.c > index 7024fc413715..68fdd5616dfe 100644 > --- a/arch/s390/kernel/ipl.c > +++ b/arch/s390/kernel/ipl.c > @@ -1929,7 +1929,8 @@ static struct shutdown_action __refdata dump_action = { > static void dump_reipl_run(struct shutdown_trigger *trigger) > { > struct lowcore *abs_lc; > - unsigned int csum; > + unsigned long ipib = 0; > + unsigned int csum = 0; > > /* > * Set REIPL_CLEAR flag in os_info flags entry indicating > @@ -1945,9 +1946,12 @@ static void dump_reipl_run(struct shutdown_trigger *trigger) > reipl_type == IPL_TYPE_UNKNOWN) > os_info_flags |= OS_INFO_FLAG_REIPL_CLEAR; > os_info_entry_add_data(OS_INFO_FLAGS_ENTRY, &os_info_flags, sizeof(os_info_flags)); > - csum = (__force unsigned int)cksm(reipl_block_actual, reipl_block_actual->hdr.len, 0); > + if (reipl_block_actual) { > + ipib = __pa(reipl_block_actual); > + csum = (__force unsigned int)cksm(reipl_block_actual, reipl_block_actual->hdr.len, 0); > + } > abs_lc = get_abs_lowcore(); > - abs_lc->ipib = __pa(reipl_block_actual); > + abs_lc->ipib = ipib; > abs_lc->ipib_checksum = csum; > put_abs_lowcore(abs_lc); > dump_run(trigger); Reviewed-by: Mikhail Zaslonko