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KVM: s390: ucontrol: Fix sca_clear_ext_call()

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When cleaning up a UCONTROL VM, sca_clear_ext_call() will touch memory
outside of the allocated ESCA block, and UCONTROL VMs don't even use
ESCA.

Fix by not touching ESCA for UCONTROL VMs, and fence the
KVM_S390_INTERRUPT ioctl altogether. Add extra checks in
sca_ext_call_pending() and sca_inject_ext_call() to make sure UCONTROL
VMs won't touch ESCA.

Fencing does not cause regressions with userspace, since UCONTROL VMs
never used KVM_S390_INTERRUPT ioctls.

Fixes: 7d43bafcff ("KVM: s390: Make provisions for ESCA utilization")
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20260803124040.126471-6-imbrenda@linux.ibm.com>
This commit is contained in:
Claudio Imbrenda 2026-08-03 14:40:32 +02:00
parent a0496b40a4
commit d301ade418
2 changed files with 19 additions and 5 deletions
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19
arch/s390/kvm/interrupt.c
View File

@ -45,13 +45,16 @@ static struct kvm_s390_gib *gib;
static int sca_ext_call_pending(struct kvm_vcpu *vcpu, int *src_id)
{
struct esca_block *sca = vcpu->kvm->arch.sca;
union esca_sigp_ctrl sigp_ctrl = sca->cpu[vcpu->vcpu_id].sigp_ctrl;
union esca_sigp_ctrl sigp_ctrl;
if (!kvm_s390_test_cpuflags(vcpu, CPUSTAT_ECALL_PEND))
return 0;
if (kvm_is_ucontrol(vcpu->kvm))
return 0;
BUG_ON(!kvm_s390_use_sca_entries());
sigp_ctrl = sca->cpu[vcpu->vcpu_id].sigp_ctrl;
if (src_id)
*src_id = sigp_ctrl.scn;
@ -60,13 +63,16 @@ static int sca_ext_call_pending(struct kvm_vcpu *vcpu, int *src_id)
static int sca_inject_ext_call(struct kvm_vcpu *vcpu, int src_id)
{
struct esca_block *sca = vcpu->kvm->arch.sca;
union esca_sigp_ctrl *sigp_ctrl = &sca->cpu[vcpu->vcpu_id].sigp_ctrl;
union esca_sigp_ctrl old_val, new_val = {.scn = src_id, .c = 1};
struct esca_block *sca = vcpu->kvm->arch.sca;
union esca_sigp_ctrl *sigp_ctrl;
int expect, rc;
BUG_ON(!kvm_s390_use_sca_entries());
if (kvm_is_ucontrol(vcpu->kvm))
return -EINVAL;
sigp_ctrl = &sca->cpu[vcpu->vcpu_id].sigp_ctrl;
old_val = READ_ONCE(*sigp_ctrl);
old_val.c = 0;
@ -84,10 +90,13 @@ static int sca_inject_ext_call(struct kvm_vcpu *vcpu, int src_id)
static void sca_clear_ext_call(struct kvm_vcpu *vcpu)
{
struct esca_block *sca = vcpu->kvm->arch.sca;
union esca_sigp_ctrl *sigp_ctrl = &sca->cpu[vcpu->vcpu_id].sigp_ctrl;
union esca_sigp_ctrl *sigp_ctrl;
if (!kvm_s390_use_sca_entries() || !vcpu->arch.initialized)
if (!kvm_s390_use_sca_entries() || !vcpu->arch.initialized || kvm_is_ucontrol(vcpu->kvm))
return;
/* Initialize after the above check, to prevent going out of bounds */
sigp_ctrl = &sca->cpu[vcpu->vcpu_id].sigp_ctrl;
kvm_s390_clear_cpuflags(vcpu, CPUSTAT_ECALL_PEND);
WRITE_ONCE(sigp_ctrl->value, 0);

5
arch/s390/kvm/kvm-s390.c
View File

@ -2934,6 +2934,9 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
case KVM_S390_INTERRUPT: {
struct kvm_s390_interrupt s390int;
r = -EINVAL;
if (kvm_is_ucontrol(kvm))
break;
r = -EFAULT;
if (copy_from_user(&s390int, argp, sizeof(s390int)))
break;
@ -5456,6 +5459,8 @@ long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, unsigned int ioctl,
struct kvm_s390_interrupt s390int;
struct kvm_s390_irq s390irq = {};
if (kvm_is_ucontrol(vcpu->kvm))
return -EINVAL;
if (copy_from_user(&s390int, argp, sizeof(s390int)))
return -EFAULT;
if (s390int_to_s390irq(&s390int, &s390irq))