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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 24 Mar 2020 07:13:05 -0000 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 02O7C2iR31523250 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 24 Mar 2020 07:12:02 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9EB71A4055; Tue, 24 Mar 2020 07:13:04 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8AFB3A4040; Tue, 24 Mar 2020 07:13:01 +0000 (GMT) Received: from oc7455500831.ibm.com (unknown [9.145.0.161]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 24 Mar 2020 07:13:01 +0000 (GMT) Subject: Re: [PATCH 1/7] KVM: Fix out of range accesses to memslots To: Sean Christopherson , Janosch Frank , Paolo Bonzini Cc: David Hildenbrand , Cornelia Huck , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Qian Cai , Peter Xu , Claudio Imbrenda References: <20200320205546.2396-1-sean.j.christopherson@intel.com> <20200320205546.2396-2-sean.j.christopherson@intel.com> From: Christian Borntraeger Autocrypt: addr=borntraeger@de.ibm.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200320205546.2396-2-sean.j.christopherson@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 20032407-0028-0000-0000-000003EA6697 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20032407-0029-0000-0000-000024AFCF2F Message-Id: <6f62f9db-a4c5-051c-2189-670d5c8707da@de.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.645 definitions=2020-03-24_01:2020-03-23,2020-03-24 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 lowpriorityscore=0 priorityscore=1501 bulkscore=0 mlxlogscore=716 impostorscore=0 suspectscore=27 clxscore=1015 spamscore=0 malwarescore=0 adultscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003240032 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 20.03.20 21:55, Sean Christopherson wrote: > Reset the LRU slot if it becomes invalid when deleting a memslot to fix > an out-of-bounds/use-after-free access when searching through memslots. > > Explicitly check for there being no used slots in search_memslots(), and > in the caller of s390's approximation variant. > > Fixes: 36947254e5f9 ("KVM: Dynamically size memslot array based on number of used slots") > Reported-by: Qian Cai > Cc: Peter Xu > Signed-off-by: Sean Christopherson > --- > arch/s390/kvm/kvm-s390.c | 3 +++ > include/linux/kvm_host.h | 3 +++ > virt/kvm/kvm_main.c | 3 +++ > 3 files changed, 9 insertions(+) > > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > index 807ed6d722dd..cb15fdda1fee 100644 > --- a/arch/s390/kvm/kvm-s390.c > +++ b/arch/s390/kvm/kvm-s390.c > @@ -2002,6 +2002,9 @@ static int kvm_s390_get_cmma(struct kvm *kvm, struct kvm_s390_cmma_log *args, Adding Claudio, but > struct kvm_memslots *slots = kvm_memslots(kvm); > struct kvm_memory_slot *ms; > > + if (unlikely(!slots->used_slots)) > + return 0; > + this looks sane and like the right fix. Acked-by: Christian Borntraeger > cur_gfn = kvm_s390_next_dirty_cmma(slots, args->start_gfn); > ms = gfn_to_memslot(kvm, cur_gfn); > args->count = 0; > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 35bc52e187a2..b19dee4ed7d9 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -1032,6 +1032,9 @@ search_memslots(struct kvm_memslots *slots, gfn_t gfn) > int slot = atomic_read(&slots->lru_slot); > struct kvm_memory_slot *memslots = slots->memslots; > > + if (unlikely(!slots->used_slots)) > + return NULL; > + > if (gfn >= memslots[slot].base_gfn && > gfn < memslots[slot].base_gfn + memslots[slot].npages) > return &memslots[slot]; > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 28eae681859f..f744bc603c53 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -882,6 +882,9 @@ static inline void kvm_memslot_delete(struct kvm_memslots *slots, > > slots->used_slots--; > > + if (atomic_read(&slots->lru_slot) >= slots->used_slots) > + atomic_set(&slots->lru_slot, 0); > + > for (i = slots->id_to_index[memslot->id]; i < slots->used_slots; i++) { > mslots[i] = mslots[i + 1]; > slots->id_to_index[mslots[i].id] = i; >