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Mon, 22 Jun 2026 16:07:40 +0000 (GMT) Received: from p-imbrenda.ehn-de.ibm.com (unknown [9.224.75.30]) by smtpav06.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 22 Jun 2026 16:07:40 +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 v5 2/9] KVM: s390: Fix dat_peek_cmma() overflow Date: Mon, 22 Jun 2026 18:07:32 +0200 Message-ID: <20260622160739.202044-3-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260622160739.202044-1-imbrenda@linux.ibm.com> References: <20260622160739.202044-1-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-Proofpoint-GUID: aUBMSCfIUPZGwNDb-5syE82M5Rg9IrNu X-Proofpoint-Spam-Info: AW1haW4tMjYwNjIyMDE1NyBTYWx0ZWRfX+A8bNY5XgVEg ZVAWz7RcX+VyrNHMpE5UUqoo8OY1lvc9Zp+yxq3eZP2lta7oa2goQwgxM3GhbtrPhG3FQUJMV0v WAaSeU+Xo/mtdzGkQ6jukhqbnPdUzmI= X-Authority-Analysis: v=2.4 cv=c62bhx9l c=1 sm=1 tr=0 ts=6a395dd1 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=0SZZOaMt82sS6LYugLYA:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjIyMDE1NyBTYWx0ZWRfXyFfF2JTM+OxC iMSSwTJeGSDlL+sHJfOj4Xp8hhGnqPo0wS2Ac1svvRVP2VqmGFiRwI22aKegUtwUw7Fh2jWGXbC Wssj7slarMMcx8V+wr4Ujg0kcO6EmcsTufCnKzliJbvh69zvR+/n3tTH+VmLzbqwvZ0b01nxPYw 1bW8ckYP4acjJVDyeGWU2cUs1o8tteIoyAG4FTSFFTn2iBjAlvwaT0RMsPtcYBbVGiF8xSimlP6 0W5wq4bd4cs+fLluUUKxwgbc2XLlZJTcaAi9um/8OrWL989i+LXUUoT+FFGJ439c9YZdlqpj/s3 vevylk14jSGAFs85+hVM5lOKLVj42/rlh1kTr8phhNo7l5MR+tQ0unUSFuI8wgp3o3PicphHbmR hefDN+Tvz1kgdCWd+G3pR7hPsHdeEGWtPqGYbY8qt33Hw5QeuKlKWE8BeiImHECzN4fJfC60Djx vKh80V7NhJpOwG7YXpg== X-Proofpoint-ORIG-GUID: aUBMSCfIUPZGwNDb-5syE82M5Rg9IrNu 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=2026-06-22_03,2026-06-22_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 impostorscore=0 adultscore=0 clxscore=1015 suspectscore=0 priorityscore=1501 phishscore=0 spamscore=0 bulkscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606220157 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