From 614a80e474b227cace52fd6e3c790554db8a396e Mon Sep 17 00:00:00 2001 From: Christian Borntraeger Date: Wed, 6 Aug 2014 16:17:58 +0200 Subject: [PATCH 1/2] KVM: s390: Fix user triggerable bug in dead code In the early days, we had some special handling for the KVM_EXIT_S390_SIEIC exit, but this was gone in 2009 with commit d7b0b5eb3000 (KVM: s390: Make psw available on all exits, not just a subset). Now this switch statement is just a sanity check for userspace not messing with the kvm_run structure. Unfortunately, this allows userspace to trigger a kernel BUG. Let's just remove this switch statement. Signed-off-by: Christian Borntraeger Reviewed-by: Cornelia Huck Reviewed-by: David Hildenbrand Cc: stable@vger.kernel.org --- arch/s390/kvm/kvm-s390.c | 13 ------------- 1 file changed, 13 deletions(-) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index ce81eb2ab76a..81b0e11521e4 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -1317,19 +1317,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) return -EINVAL; } - switch (kvm_run->exit_reason) { - case KVM_EXIT_S390_SIEIC: - case KVM_EXIT_UNKNOWN: - case KVM_EXIT_INTR: - case KVM_EXIT_S390_RESET: - case KVM_EXIT_S390_UCONTROL: - case KVM_EXIT_S390_TSCH: - case KVM_EXIT_DEBUG: - break; - default: - BUG(); - } - vcpu->arch.sie_block->gpsw.mask = kvm_run->psw_mask; vcpu->arch.sie_block->gpsw.addr = kvm_run->psw_addr; if (kvm_run->kvm_dirty_regs & KVM_SYNC_PREFIX) { From ab3f285f227fec62868037e9b1b1fd18294a83b8 Mon Sep 17 00:00:00 2001 From: Christian Borntraeger Date: Tue, 19 Aug 2014 16:19:35 +0200 Subject: [PATCH 2/2] KVM: s390/mm: try a cow on read only pages for key ops The PFMF instruction handler blindly wrote the storage key even if the page was mapped R/O in the host. Lets try a COW before continuing and bail out in case of errors. Signed-off-by: Christian Borntraeger Reviewed-by: Dominik Dingel Cc: stable@vger.kernel.org --- arch/s390/mm/pgtable.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c index 19daa53a3da4..5404a6261db9 100644 --- a/arch/s390/mm/pgtable.c +++ b/arch/s390/mm/pgtable.c @@ -986,11 +986,21 @@ int set_guest_storage_key(struct mm_struct *mm, unsigned long addr, pte_t *ptep; down_read(&mm->mmap_sem); +retry: ptep = get_locked_pte(current->mm, addr, &ptl); if (unlikely(!ptep)) { up_read(&mm->mmap_sem); return -EFAULT; } + if (!(pte_val(*ptep) & _PAGE_INVALID) && + (pte_val(*ptep) & _PAGE_PROTECT)) { + pte_unmap_unlock(*ptep, ptl); + if (fixup_user_fault(current, mm, addr, FAULT_FLAG_WRITE)) { + up_read(&mm->mmap_sem); + return -EFAULT; + } + goto retry; + } new = old = pgste_get_lock(ptep); pgste_val(new) &= ~(PGSTE_GR_BIT | PGSTE_GC_BIT |