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Wed, 5 Aug 2026 11:16:19 +0000 (GMT) From: Stefan Haberland To: Jens Axboe Cc: linux-block@vger.kernel.org, Jan Hoeppner , linux-s390@vger.kernel.org, Heiko Carstens , Vasily Gorbik , Christian Borntraeger Subject: [PATCH 19/19] s390/dasd: Read cached unit address and LSS in the CCW build path Date: Wed, 5 Aug 2026 13:16:12 +0200 Message-ID: <20260805111612.1285190-20-sth@linux.ibm.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260805111612.1285190-1-sth@linux.ibm.com> References: <20260805111612.1285190-1-sth@linux.ibm.com> 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=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODA1MDA4NiBTYWx0ZWRfX1aZpoEsr/aXP z1KPLIkTxBwhhkC5pkHnTlt31P55e2cmceEo8xE5sjBp/tiykzBw6kWDvMu4OFbUkHr4i0ouru+ RuSJRDddQyhmLsNVWMh74slAuNduERkK24xx3umrNhteC9+MvlEzO9ZOkqqsQujpjG1+7zeUJuA FEpt8W17NcaI3qpYSOYsjy+RxYAI87/AfPtE5qFvtsWFtTWdEgiRpKY89IhUkp81ElQSjmCefl+ J9zruJB1282ZVjQcvPUr32EbQ4sNOJLjXiW9iorIiKDSvWWQt1sxaPyMaP3SabPEM2H+dgcVjqY P7fp/nIncldvC21L706LIyy1ADB0ENntLk2ZraN+Q4x9soBlx/aQNQqlqAGz+3AGO5OplWTO/HJ GPLUVBfDPHnqRm34+5Qf5EfQeJYZADjyrOCqGsboLHam0q74ZlWo5hkqbOvPZNe8RWr9N0I8ycJ RJuqNl1ZQ+YUsvRR4Aw== X-Authority-Analysis: v=2.4 cv=WIFPmHsR c=1 sm=1 tr=0 ts=6a731b8a cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=OPmwjG8nANrwyK2qht4A:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: vWhVk19es2RHa--tNyAjOLz5crhkwLit X-Proofpoint-ORIG-GUID: vWhVk19es2RHa--tNyAjOLz5crhkwLit X-Proofpoint-Spam-Info: AW1haW4tMjYwODA1MDA4NiBTYWx0ZWRfX3kVRD0NQcISJ Hx6O1/j3zfnimj6k9EcUcN+MkD+k3i9pB8dImcjM2uRmlniwqvVsaoyVwv9F/T9cyWVKZc6hxKC nbqQlcHRd4MuxrhGofo3iBOELhmf0HA= 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=2026-08-05_03,2026-08-04_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 lowpriorityscore=0 priorityscore=1501 phishscore=0 malwarescore=0 suspectscore=0 clxscore=1015 impostorscore=0 bulkscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608050086 The CCW build path (prefix_LRE, the full-track prefix and dso_ras) read the base address and LSS straight from conf.ned. That buffer is freed and reallocated by the reload worker (do_reload_device - dasd_eckd_read_conf - dasd_eckd_clear_conf_data), so a configuration change concurrent with I/O can free conf.ned while a request is being built. Use-after-free reported by KASAN in prefix_LRE. Read the cached copies instead. The unit address is already kept in uid.real_unit_addr, and the LSS is now cached in ned_lss. Both are refreshed under the ccwdev lock in dasd_eckd_generate_uid whenever the configuration is (re)read. Also fix for prepare for read subsystem data (prssd) users. Reviewed-by: Jan Höppner Signed-off-by: Stefan Haberland --- drivers/s390/block/dasd_eckd.c | 26 ++++++++++++++++---------- drivers/s390/block/dasd_eckd.h | 8 ++++++++ 2 files changed, 24 insertions(+), 10 deletions(-) diff --git a/drivers/s390/block/dasd_eckd.c b/drivers/s390/block/dasd_eckd.c index 5c1f328b7c8d..fd23ac25a7da 100644 --- a/drivers/s390/block/dasd_eckd.c +++ b/drivers/s390/block/dasd_eckd.c @@ -589,8 +589,9 @@ static int prefix_LRE(struct ccw1 *ccw, struct PFX_eckd_data *pfxdata, return -EINVAL; } pfxdata->format = format; - pfxdata->base_address = basepriv->conf.ned->unit_addr; - pfxdata->base_lss = basepriv->conf.ned->ID; + /* cached copies - conf.ned may be freed under us by the reload worker */ + pfxdata->base_address = READ_ONCE(basepriv->ned_ua); + pfxdata->base_lss = READ_ONCE(basepriv->ned_lss); pfxdata->validity.define_extent = 1; /* private uid is kept up to date, conf_data may be outdated */ @@ -807,6 +808,9 @@ static int dasd_eckd_generate_uid(struct dasd_device *device) return -ENODEV; spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags); create_uid(&private->conf, &private->uid); + /* cache LSS and unit address for the lockless CCW-build path */ + WRITE_ONCE(private->ned_lss, private->conf.ned->ID); + WRITE_ONCE(private->ned_ua, private->conf.ned->unit_addr); spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags); return 0; } @@ -1632,8 +1636,8 @@ static int dasd_eckd_read_vol_info(struct dasd_device *device) prssdp = cqr->data; prssdp->order = PSF_ORDER_PRSSD; prssdp->suborder = PSF_SUBORDER_VSQ; /* Volume Storage Query */ - prssdp->lss = private->conf.ned->ID; - prssdp->volume = private->conf.ned->unit_addr; + prssdp->lss = READ_ONCE(private->ned_lss); + prssdp->volume = READ_ONCE(private->ned_ua); ccw = cqr->cpaddr; ccw->cmd_code = DASD_ECKD_CCW_PSF; @@ -4250,8 +4254,9 @@ dasd_eckd_dso_ras(struct dasd_device *device, struct dasd_block *block, if (!req && features->feature[56] & 0x01 && !copy_relation) ras_data->op_flags.guarantee_init = 1; - ras_data->lss = private->conf.ned->ID; - ras_data->dev_addr = private->conf.ned->unit_addr; + /* cached copies - conf.ned may be freed under us by the reload worker */ + ras_data->lss = READ_ONCE(private->ned_lss); + ras_data->dev_addr = READ_ONCE(private->ned_ua); ras_data->nr_exts = nr_exts; if (by_extent) { @@ -4822,8 +4827,9 @@ static int prepare_itcw(struct itcw *itcw, lredata = &pfxdata->locate_record; pfxdata->format = 1; /* PFX with LRE */ - pfxdata->base_address = basepriv->conf.ned->unit_addr; - pfxdata->base_lss = basepriv->conf.ned->ID; + /* cached copies - conf.ned may be freed under us by the reload worker */ + pfxdata->base_address = READ_ONCE(basepriv->ned_ua); + pfxdata->base_lss = READ_ONCE(basepriv->ned_lss); pfxdata->validity.define_extent = 1; /* private uid is kept up to date, conf_data may be outdated */ @@ -6905,8 +6911,8 @@ static int dasd_eckd_query_host_access(struct dasd_device *device, prssdp->order = PSF_ORDER_PRSSD; prssdp->suborder = PSF_SUBORDER_QHA; /* query host access */ /* LSS and Volume that will be queried */ - prssdp->lss = private->conf.ned->ID; - prssdp->volume = private->conf.ned->unit_addr; + prssdp->lss = READ_ONCE(private->ned_lss); + prssdp->volume = READ_ONCE(private->ned_ua); /* all other bytes of prssdp must be zero */ ccw = cqr->cpaddr; diff --git a/drivers/s390/block/dasd_eckd.h b/drivers/s390/block/dasd_eckd.h index 30745f62402b..8e6f09e9ca7e 100644 --- a/drivers/s390/block/dasd_eckd.h +++ b/drivers/s390/block/dasd_eckd.h @@ -736,6 +736,14 @@ struct dasd_eckd_private { /* alias management */ struct dasd_uid uid; + /* + * Cached copies of conf.ned->ID (the LSS) and conf.ned->unit_addr, + * refreshed under ccwdev_lock. Kept outside uid because create_uid() + * memsets uid before repopulating it, which would expose a transient + * zero to the lockless CCW-build readers. + */ + __u8 ned_lss; + __u8 ned_ua; struct alias_pav_group *pavgroup; struct alias_lcu *lcu; int count; -- 2.53.0