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Fri, 23 Oct 2026 09:21:24 +0000 (GMT) Received: from tuxmaker.lnxne.boe (unknown [9.87.85.9]) by smtpav03.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 23 Oct 2026 09:21:24 +0000 (GMT) From: Stefan Haberland To: linux-s390@vger.kernel.org Cc: Jan Hoeppner , Eduard Shishkin Subject: [PATCH 3/3] s390/dasd: Don't trust userspace-supplied result field in format check Date: Fri, 23 Oct 2026 11:21:18 +0200 Message-ID: <20261023092118.3152286-4-sth@linux.ibm.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261023092118.3152286-1-sth@linux.ibm.com> References: <20261023092118.3152286-1-sth@linux.ibm.com> X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=X63Hu2Te c=1 sm=1 tr=0 ts=6adb2718 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=c92rfblmAAAA:8 a=VnNF1IyMAAAA:8 a=VwQbUJbxAAAA:8 a=T2NVWVN1rChL1tsUD_4A:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=GvGzcOZaWPEFPQC_NcjD:22 X-Proofpoint-ORIG-GUID: VNO0QABkWX_qHJmX-CeQWUIW2Jo86HsJ X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDIzMDAzNiBTYWx0ZWRfX1tYm6XhP9E0x tXnPoUco0jOBASkJkoWSZ/Qe2veOOLh/brSCO6YSjfsBnM+QORbmJ8w+jAqDSZ+6+KVnUh3YQ73 5pa7NU+KdR3edOjWBDJbeRpY2C0hShxoKD9tVh8/RMYUv/rcI5Sucq3lQFVlb87kGw2wxWX0WXw Upu4kNLiHZS7Db7io2nYExEfVuPrPjuc0E88ZquJthMBt1ksq6o8pr/wq4pTTj8DPQBMMd6H5hE 8asTBLqDht5vPD6DwQnq17EvvLqll2Fe7trq/PCnbVQ9GdoB9+AOihtXeC6v1jrarZAnrcYKyzq wuTRSa61ZMDWLsbxXKo7/Q8foj3Xtk3epL4WFGd7l5g96xLbiwV84CuB+6Wt5EYkjSDMmFXeTYS jCGEek/wx3racr4toKn7wajekcOzgNJSZ8/ghfa873Emp1WRuKOsYnAw7nCq+dMTNrm763Q6akk nuaQQ91zCNvSF67Peww== X-Proofpoint-Spam-Info: AW1haW4tMjYxMDIzMDAzNiBTYWx0ZWRfX0S3uRMwhQJs0 ZMGchZrskIHdbQ7RtvP70bPwX+B+cGGNqgctuPlfm8dY5NyCRqcdayuP7shpwCmnAAdgs7C6n/o aamW/FtXgsnC6dsuUcUMXbqy/4Riqos= X-Proofpoint-GUID: VNO0QABkWX_qHJmX-CeQWUIW2Jo86HsJ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-10-23_02,2026-10-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 phishscore=0 bulkscore=0 adultscore=0 malwarescore=0 clxscore=1015 spamscore=0 impostorscore=0 lowpriorityscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610190000 definitions=main-2610230036 BIODASDCHECKFMT used to copy the entire format_check_t struct from userspace, including the result/unit/rec/num_records/blksize/ key_length fields that are output fields only. dasd_eckd_format_evaluate_tracks() relies on cdata->result being zero to decide whether to apply an index correction (i--/pos--) after a successful check. A caller that pre-sets result to a non-zero value can suppress that correction, leaving pos advanced past the last valid entry; the (partially out-of-bounds) fmt_buffer[pos] fields are then copied back to userspace, leaking heap contents. Only expect is an Input field; copy just that member in and zero the rest of cdata. Fixes: 8fd575200db5 ("s390/dasd: Add new ioctl BIODASDCHECKFMT") Reported-by: Sashiko Closes: https://sashiko.dev/#/patchset/20260722103704.1709668-1-sth@linux.ibm.com Cc: stable@vger.kernel.org #4.7 Reviewed-by: Jan Höppner Signed-off-by: Stefan Haberland --- drivers/s390/block/dasd_ioctl.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/s390/block/dasd_ioctl.c b/drivers/s390/block/dasd_ioctl.c index e5b8b413f5ab..2f2ec2bea333 100644 --- a/drivers/s390/block/dasd_ioctl.c +++ b/drivers/s390/block/dasd_ioctl.c @@ -303,7 +303,9 @@ static int dasd_ioctl_check_format(struct block_device *bdev, void __user *argp) goto out_err; } - if (copy_from_user(&cdata, argp, sizeof(cdata))) { + /* copy only input fields, clear the rest */ + memset(&cdata, 0, sizeof(cdata)); + if (copy_from_user(&cdata.expect, argp, sizeof(cdata.expect))) { rc = -EFAULT; goto out_err; } -- 2.53.0