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Tue, 2 Jun 2026 14:23:58 +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 Subject: [PATCH v3 08/10] KVM: s390: Prevent memslots outside the ASCE range Date: Tue, 2 Jun 2026 16:23:54 +0200 Message-ID: <20260602142356.169458-9-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260602142356.169458-1-imbrenda@linux.ibm.com> References: <20260602142356.169458-1-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-Details-Enc: AW1haW4tMjYwNjAyMDEzNiBTYWx0ZWRfXx1M6mtGQHjYQ cPvFsMS/75/1Vkz4t1G5JIoQNZThtNKRY+AReSTiFalu0axb2N1slOpTqsmXcJjBDzdyicyG8Bs wCjzl/82CmGMejnD1aaFSeZoJbvga9fz/JngTWowSjmH6jEuwm0pAJIwMLZmJTuPNtohltVb7k2 BN05esSzG6DpHVv/wc8/L0caycsxAS2fdqLkwskSmrKoaE4S5RJls0Yaqn4UQn2qvm75wtCi1pa +3c+5+jUl0eZgRLsTNj+kmX50nGwkLUfBTxPrfEdUrkxMlK5b115G2Zyj3WD0HsItZmSDpW/BN5 sxvGH+fVp3c7L0GwbMOSbwdJNyLfYz5+mXo3dYTzxgAOiNpHIhynULlkP83T1D1slKqAHslSW8W gBKEmyxJBKXGU95LBd5XFXdMd8FgS6akorc7+gTFBVtfJUXYMIf3ttWc51cMYn0fGek5OHZh+Jy iRZMhPN4l1NYSqF1Bng== X-Proofpoint-GUID: 5QzxN7wq_B-ilkocnZqqCDq1cw1cRM6o X-Proofpoint-ORIG-GUID: 5QzxN7wq_B-ilkocnZqqCDq1cw1cRM6o X-Authority-Analysis: v=2.4 cv=DZknbPtW c=1 sm=1 tr=0 ts=6a1ee785 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=1rJwsmJvMo9JdAIlmdgA:9 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=2026-06-02_02,2026-05-28_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 clxscore=1015 suspectscore=0 impostorscore=0 lowpriorityscore=0 phishscore=0 malwarescore=0 priorityscore=1501 bulkscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606020136 With KVM_S390_VM_MEM_LIMIT_SIZE, userspace can set the highest address allowed for the VM. Creating a memslot that lies over the maximum address does not make sense and is only a potential source of bugs. Prevent creation of memslots over the maximum address, and prevent the maximum address from being reduced below the end of existing memslots. Signed-off-by: Claudio Imbrenda --- arch/s390/kvm/kvm-s390.c | 33 ++++++++++++++++++++++++++++----- 1 file changed, 28 insertions(+), 5 deletions(-) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index e09960c2e6ed..ffb20a64d328 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -999,7 +999,10 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att break; } case KVM_S390_VM_MEM_LIMIT_SIZE: { + struct kvm_memslots *slots; + struct kvm_memory_slot *ms; unsigned long new_limit; + int bkt; if (kvm_is_ucontrol(kvm)) return -EINVAL; @@ -1007,6 +1010,9 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att if (get_user(new_limit, (u64 __user *)attr->addr)) return -EFAULT; + guard(mutex)(&kvm->lock); + + new_limit = ALIGN(new_limit, HPAGE_SIZE); if (kvm->arch.mem_limit != KVM_S390_NO_MEM_LIMIT && new_limit > kvm->arch.mem_limit) return -E2BIG; @@ -1014,12 +1020,27 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att if (!new_limit) return -EINVAL; - ret = -EBUSY; - if (!kvm->created_vcpus) - ret = gmap_set_limit(kvm->arch.gmap, gpa_to_gfn(new_limit)); + if (kvm->created_vcpus) + return -EBUSY; + + ret = 0; + scoped_guard(mutex, &kvm->slots_lock) { + slots = kvm_memslots(kvm); + if (slots && !kvm_memslots_empty(slots)) { + kvm_for_each_memslot(ms, bkt, slots) { + if (gpa_to_gfn(new_limit) < ms->base_gfn + ms->npages) { + ret = -EBUSY; + break; + } + } + } + if (!ret) + ret = gmap_set_limit(kvm->arch.gmap, gpa_to_gfn(new_limit)); + } + if (ret) + break; VM_EVENT(kvm, 3, "SET: max guest address: %lu", new_limit); - VM_EVENT(kvm, 3, "New guest asce: 0x%p", - (void *)kvm->arch.gmap->asce.val); + VM_EVENT(kvm, 3, "New guest asce: 0x%p", (void *)kvm->arch.gmap->asce.val); break; } default: @@ -5672,6 +5693,8 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, return -EINVAL; if ((new->base_gfn + new->npages) * PAGE_SIZE > kvm->arch.mem_limit) return -EINVAL; + if (!asce_contains_gfn(kvm->arch.gmap->asce, new->base_gfn + new->npages - 1)) + return -EINVAL; } if (!kvm->arch.migration_mode) -- 2.54.0