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Mon, 13 Jul 2026 15:09:00 +0000 (GMT) Received: from p-imbrenda.ibmuc.com (unknown [9.87.153.197]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 13 Jul 2026 15:09:00 +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 v2 3/7] KVM: s390: Fix race in __do_essa() Date: Mon, 13 Jul 2026 17:08:53 +0200 Message-ID: <20260713150857.269954-4-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260713150857.269954-1-imbrenda@linux.ibm.com> References: <20260713150857.269954-1-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: TO4sAh3WbSf6kSX7jyysdujzLHDVR3D- X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzEzMDE1MyBTYWx0ZWRfX7H0eQHzXzZqn sVxVujsqVur/AxQCZq1KDOy4jVsWOcaBxupHqoT9ditmphEmGEt2L4mOMtnbyMUvS8EmXCTjFub gT0aEJCf6VlrPkb3HE9kr1Vw+terFvhOE9TLsl7Iy3DnoWz2r47pDmWcw8ysMZNQT5Ho0Lfuxk1 N+ghQAZWTQMDDF8sHIDAyrrpY1H7QHt8MTSUR+GrpjRw9nIkghd9TuyeaNarEOOWndOQfyHHcv6 +Gj6K5ZUt8Ip4k9MxUF4THdxwtHVt1Fl4LUgF776N8aaRl9x9FROEpwIjjT8bnV7a8fl0qh5wzZ qs/R0ZjlLTx8uuU/csFBemImtkpBLgoAsB+iBKUiKM1k5U1UCFA73PCIPexJLOjIpBRzJVAa5/A 80hocktG0pi3IJXTsPpLsYbx0tiOpsS5pcUwu1eu8a+YEAX08vCrMsNQbNNPUXvb52v9+oOTy4l VG0MGEGjSU7fTIdzGkw== X-Authority-Analysis: v=2.4 cv=XJoAjwhE c=1 sm=1 tr=0 ts=6a54ff94 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=AI3xc-Vg5h5KuinStKkA:9 X-Proofpoint-ORIG-GUID: TO4sAh3WbSf6kSX7jyysdujzLHDVR3D- X-Proofpoint-Spam-Info: AW1haW4tMjYwNzEzMDE1MyBTYWx0ZWRfX8QjEh69uuF2O RCq++iUarQJNEw7UWOTd87oGBO6e4GTzihp7u0tAMSMu5rPgp9DgmQ1Jv3cgm7PrgH139O103Hi pZqtmt8YgKgxd7Un6dYwgZ3Yb/ZTrpI= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-13_03,2026-07-10_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 adultscore=0 bulkscore=0 phishscore=0 lowpriorityscore=0 priorityscore=1501 impostorscore=0 clxscore=1015 spamscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607130153 An unlikely race between __do_essa() and kvm_s390_vm_start_migration(), kvm_s390_vm_stop_migration(), or dat_get_cmma() was possible. Fix by locking kvm->slots_lock. Since this is not a hot path, the overhead of an additional mutex is negligible. Fixes: e38c884df921 ("KVM: s390: Switch to new gmap") Signed-off-by: Claudio Imbrenda --- arch/s390/kvm/kvm-s390.c | 9 ++++----- arch/s390/kvm/priv.c | 5 +++-- 2 files changed, 7 insertions(+), 7 deletions(-) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 53691aaf6534..9e3b8b5c6aa6 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -1298,7 +1298,8 @@ static int kvm_s390_vm_set_migration(struct kvm *kvm, { int res = -ENXIO; - mutex_lock(&kvm->slots_lock); + guard(mutex)(&kvm->slots_arch_lock); + switch (attr->attr) { case KVM_S390_VM_MIGRATION_START: res = kvm_s390_vm_start_migration(kvm); @@ -1309,7 +1310,6 @@ static int kvm_s390_vm_set_migration(struct kvm *kvm, default: break; } - mutex_unlock(&kvm->slots_lock); return res; } @@ -2996,9 +2996,8 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) r = -EFAULT; if (copy_from_user(&args, argp, sizeof(args))) break; - mutex_lock(&kvm->slots_lock); - r = kvm_s390_get_cmma_bits(kvm, &args); - mutex_unlock(&kvm->slots_lock); + scoped_guard(mutex, &kvm->slots_arch_lock) + r = kvm_s390_get_cmma_bits(kvm, &args); if (!r) { r = copy_to_user(argp, &args, sizeof(args)); if (r) diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c index ad0ddc433a73..d4c91e416167 100644 --- a/arch/s390/kvm/priv.c +++ b/arch/s390/kvm/priv.c @@ -1260,8 +1260,9 @@ static int handle_essa(struct kvm_vcpu *vcpu) /* Retry the ESSA instruction */ kvm_s390_retry_instr(vcpu); } else { - scoped_guard(read_lock, &vcpu->kvm->mmu_lock) - i = __do_essa(vcpu, orc); + scoped_guard(mutex, &vcpu->kvm->slots_arch_lock) + scoped_guard(read_lock, &vcpu->kvm->mmu_lock) + i = __do_essa(vcpu, orc); if (i < 0) return i; /* Account for the possible extra cbrl entry */ -- 2.55.0