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Fri, 31 Jul 2026 13:01:45 +0000 (GMT) Received: from p-imbrenda.ibmuc.com (unknown [9.111.4.62]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 31 Jul 2026 13:01:45 +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 v7 07/14] KVM: s390: Fix race in __do_essa() Date: Fri, 31 Jul 2026 15:01:31 +0200 Message-ID: <20260731130138.173983-8-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260731130138.173983-1-imbrenda@linux.ibm.com> References: <20260731130138.173983-1-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: ycC_rVo4QATofPMrvJQLvLJTTsdS_R79 X-Proofpoint-ORIG-GUID: ycC_rVo4QATofPMrvJQLvLJTTsdS_R79 X-Proofpoint-Spam-Info: AW1haW4tMjYwNzMxMDA5NiBTYWx0ZWRfX53uG7PlvNnpX gIPgpnh62xS13mWf/axnGxBD8ObcTCoiu0HQ6tipFaYAhQQ3O3xXOb//p3UOL9iOUjJDD7Bb/dY 22qNmTH82KeJN5K1YqrqgAfKIXmeKiA= X-Authority-Analysis: v=2.4 cv=dYuwG3Xe c=1 sm=1 tr=0 ts=6a6c9cc1 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VnNF1IyMAAAA:8 a=vVGDtJNaOgRaVfleRDgA:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzMxMDA5NiBTYWx0ZWRfX1q/Od4B3ur17 ZIvJT6Gd/Iyi2BDztOq16Nf3y710TlXLIHWdQpjcM4VwzmBuLtwLIuQBTxNU1AY/Nw3+lai1Ijg bZMnjihpJ+jlKX1c7uvKFnSfQ9zJCyXSL2T7e2d4hvb1BnMnbYbcqBdi+S4J6ugmUQP7WiiGSXg hmAV1jVD4gMAi0Ai7c8DuT9zzOZPEwzpFwg7e6B872CYElFPMw2KymX1bQ1Ngq+Q0+bYdF1qkBt +PP0dzeckIc+1RY4TAICOWJ3cJznyfs5/hlgRf2bFyUsrNwbLU/S273rh9tqibPA8gtsnFPlIUr EloKvebXReO15yr2r/PYhDhF/En0TohOYcw/gSmTiKMRXzyVklZbHOsqB2Ap/VfvaN+kCvAKdGz irTkL4TxQHPktHetD0nBf5iqlhFllIpbsQErg5FTWaEdpNUj0QM5cdVSeN5CzlpCpKzJKqjzbqk D2mFZgtSj+vmAe+0eTw== 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=2026-07-31_04,2026-07-30_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 clxscore=1015 phishscore=0 malwarescore=0 spamscore=0 lowpriorityscore=0 bulkscore=0 suspectscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607310096 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_arch_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 | 20 ++++++++++---------- arch/s390/kvm/priv.c | 5 +++-- 2 files changed, 13 insertions(+), 12 deletions(-) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index e162efaa35b8..e5c5e9f61cb2 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -1219,8 +1219,8 @@ static void kvm_s390_sync_request_broadcast(struct kvm *kvm, int req) /* * Must be called with kvm->srcu held to avoid races on memslots, and with - * kvm->slots_lock to avoid races with ourselves, kvm_s390_vm_stop_migration(), - * and kvm_s390_get_cmma_bits(). + * kvm->slots_arch_lock to avoid races with ourselves, + * kvm_s390_vm_stop_migration(), and kvm_s390_get_cmma_bits(). */ static int kvm_s390_vm_start_migration(struct kvm *kvm) { @@ -1265,7 +1265,7 @@ static int kvm_s390_vm_start_migration(struct kvm *kvm) } /* - * Must be called with kvm->slots_lock to avoid races with ourselves, + * Must be called with kvm->slots_arch_lock to avoid races with ourselves, * kvm_s390_vm_start_migration() and kvm_s390_get_cmma_bits(). */ static int kvm_s390_vm_stop_migration(struct kvm *kvm) @@ -1300,7 +1300,9 @@ static int kvm_s390_vm_set_migration(struct kvm *kvm, { int res = -ENXIO; - mutex_lock(&kvm->slots_lock); + guard(srcu)(&kvm->srcu); + guard(mutex)(&kvm->slots_arch_lock); + switch (attr->attr) { case KVM_S390_VM_MIGRATION_START: res = kvm_s390_vm_start_migration(kvm); @@ -1311,7 +1313,6 @@ static int kvm_s390_vm_set_migration(struct kvm *kvm, default: break; } - mutex_unlock(&kvm->slots_lock); return res; } @@ -3001,9 +3002,8 @@ 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) @@ -3017,9 +3017,9 @@ 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); + mutex_lock(&kvm->slots_arch_lock); r = kvm_s390_set_cmma_bits(kvm, &args); - mutex_unlock(&kvm->slots_lock); + mutex_unlock(&kvm->slots_arch_lock); break; } case KVM_S390_PV_COMMAND: { diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c index ea5a99537346..b1ba24c346ef 100644 --- a/arch/s390/kvm/priv.c +++ b/arch/s390/kvm/priv.c @@ -1261,8 +1261,9 @@ 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