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Tue, 16 Jun 2026 16:51:13 +0000 (GMT) Received: from p-imbrenda.ibmuc.com (unknown [9.111.66.4]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 16 Jun 2026 16:51:13 +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 v3 2/4] KVM: s390: Fix dat_peek_cmma() overflow Date: Tue, 16 Jun 2026 18:51:08 +0200 Message-ID: <20260616165110.360921-3-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260616165110.360921-1-imbrenda@linux.ibm.com> References: <20260616165110.360921-1-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-Spam-Info: AW1haW4tMjYwNjE2MDE3MyBTYWx0ZWRfX6ZimWGNpBdXb rWYn7epGKwkDHOehj9eJOZy5aDwfAw/T+lFKnV31MvKXbcXROTEvbfO/oNYYvYObzRA9B5YwWcM DoQv7TxXsx5ruLsnFDwJMAg1QOKwx4o= X-Proofpoint-ORIG-GUID: P0_KTZl33TSH1MKpOByAy3QdhO0AE03k X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjE2MDE3MyBTYWx0ZWRfX4XJnoHewgU7M CeQQXbn6IqqONkHs7pWy2mm29AgXS57dazggUO7AQauw61h+3NdzKG4Mc7QznFVpo8zHQj4atne ilAUsel2r5+vWuFwj65stBIh29XbTNDVqH5Tf4mC9Js+qlzZ9Y47fJutCXJjHSnCUT0+n050BtO 0kUEGaZgbUPgvHXIj+kZWrabsTFGcDtWSuZfpoR0G4LYO70C3wQzibT1/O/UsqoYZ11Ir1dmgma hwS7o8cuWkdfPy6sbqX/RiI1W+FBRcRwLu/kOovxQcly50DvjQo6rMDFsITGLakO1SLtLekQzpD YugEHRqwIeuN4Ftk0CKea5ZmvbaAaT3CubjL0bZZplmKM+sInxXT2S92vvNfxGlRhPSs9pl0PNI ZxVjpXZz8cDgzVtgy0LyWbpwx1J1DCOKLa7J7kXl4p8ZRufYVj4c+dAbD3IiZGqtZ1Gqy42UKC6 eB8+2/P+ozGsA3wExGQ== X-Authority-Analysis: v=2.4 cv=U9uiy+ru c=1 sm=1 tr=0 ts=6a317f07 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VnNF1IyMAAAA:8 a=0SZZOaMt82sS6LYugLYA:9 X-Proofpoint-GUID: P0_KTZl33TSH1MKpOByAy3QdhO0AE03k 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=2026-06-16_05,2026-06-15_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 impostorscore=0 bulkscore=0 phishscore=0 priorityscore=1501 clxscore=1015 adultscore=0 malwarescore=0 suspectscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606040000 definitions=main-2606160173 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