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Tue, 23 Jun 2026 15:33:31 +0000 (GMT) Received: from p-imbrenda.ehn-de.ibm.com (unknown [9.224.75.30]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 23 Jun 2026 15:33:31 +0000 (GMT) From: Claudio Imbrenda To: linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, david@kernel.org, seiden@linux.ibm.com, nrb@linux.ibm.com, schlameuss@linux.ibm.com, gra@linux.ibm.com, hca@linux.ibm.com, gerald.schaefer@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, svens@linux.ibm.com Subject: [PATCH v6 02/10] KVM: s390: Fix dat_peek_cmma() overflow Date: Tue, 23 Jun 2026 17:33:23 +0200 Message-ID: <20260623153331.233784-3-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260623153331.233784-1-imbrenda@linux.ibm.com> References: <20260623153331.233784-1-imbrenda@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=X4Ni7mTe c=1 sm=1 tr=0 ts=6a3aa751 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=0SZZOaMt82sS6LYugLYA:9 X-Proofpoint-Spam-Info: AW1haW4tMjYwNjIzMDEyNiBTYWx0ZWRfX6piAANn+p8Hf 0OwpT8SwIT4eUBDeYhkcorVRIod7PuHdmaZ8bYhrU9YNl3KVwm8XOKin+rMkF5H/d6VIc91NL3Q NhU1urThTt3Yu3mq2+dtIVfUvjViQuc= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjIzMDEyNiBTYWx0ZWRfXyZGtlZL8bXiy qbOlU/NWcFe6qVuPxUeE6jFLn/Di+gwa4vg6qj+a5mRJwy2invIElqe0mkognGrq1llf4hhPaot gaP9hCLTHggYI/xy6YfdHbey9DaqJKbhE0zf4R+HxEYOb/maM7isyOJHNSmCwdGR9Btk58aEzlM F9JIzaWMiUvD63oLUigh7kxWXMctGVjy7HV6mVdQ11fK6kdmSexcjPb1IdlTV3lE9PVEejZ+h+C fzTchlLeDwXtEv5PkC6ffpvFqRc2Qo+YIhscn5jaeXhFSopQSPKOZNQey58mgRLuMDdPSCqAd/6 V+jFZHzopCfFUiOJS0NkjBgYnIBqA2/Rs8ku+m3NaK8YTbPd+rb+jIqb+IVl3qDRwWTUWfwrFhx V4cQm0bsjDe092FW0dZvfBFVQeh9NIBONA1tPAFYUb+ebHscY2/Zw3v6IktPbtRcClcRk1EHD76 BhU+tj+ODxLPi/L+u+w== X-Proofpoint-ORIG-GUID: vWkvv8e1K4gHn2Qt5r4OGV5NmLGgOY71 X-Proofpoint-GUID: vWkvv8e1K4gHn2Qt5r4OGV5NmLGgOY71 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-23_03,2026-06-23_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 bulkscore=0 suspectscore=0 spamscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 clxscore=1015 adultscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606230126 If userspace passes a start address that is out of bounds, _dat_walk_gfn_range() will fail with -EFAULT, but state.end will not be touched and will stay 0. This will cause *count to underflow and report a very high number, and the function will end up erroneously reporting success. Fix by only setting *count if the end address is not smaller than the starting address. This way invalid starting addresses will correctly return -EFAULT and *count will correctly indicate that no values have been returned. Fixes: 7b368470e1a4 ("KVM: s390: KVM page table management functions: CMMA") Signed-off-by: Claudio Imbrenda --- arch/s390/kvm/dat.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/s390/kvm/dat.c b/arch/s390/kvm/dat.c index 4a41c0247ffa..cffac7782c4b 100644 --- a/arch/s390/kvm/dat.c +++ b/arch/s390/kvm/dat.c @@ -1209,7 +1209,7 @@ int dat_peek_cmma(gfn_t start, union asce asce, unsigned int *count, u8 *values) int rc; rc = _dat_walk_gfn_range(start, start + *count, asce, &ops, DAT_WALK_DEFAULT, &state); - *count = state.end - start; + *count = state.end >= start ? state.end - start : 0; /* Return success if at least one value was saved, otherwise an error. */ return (rc == -EFAULT && *count > 0) ? 0 : rc; } -- 2.54.0