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authorJanis Schoetterl-Glausch <scgl@linux.ibm.com>2022-03-11 18:00:40 +0100
committerHeiko Carstens <hca@linux.ibm.com>2022-05-02 19:45:03 +0200
commitb5d1274409d0eec6d826f65d6dafebf9d77a1b99 (patch)
tree625cd38eba44cc56d11b7360690ad83feed99af6
parent8b202ee218395319aec1ef44f72043e1fbaccdd6 (diff)
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KVM: s390: Fix lockdep issue in vm memop
Issuing a memop on a protected vm does not make sense, neither is the memory readable/writable, nor does it make sense to check storage keys. This is why the ioctl will return -EINVAL when it detects the vm to be protected. However, in order to ensure that the vm cannot become protected during the memop, the kvm->lock would need to be taken for the duration of the ioctl. This is also required because kvm_s390_pv_is_protected asserts that the lock must be held. Instead, don't try to prevent this. If user space enables secure execution concurrently with a memop it must accecpt the possibility of the memop failing. Still check if the vm is currently protected, but without locking and consider it a heuristic. Fixes: ef11c9463ae0 ("KVM: s390: Add vm IOCTL for key checked guest absolute memory access") Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com> Reviewed-by: Janosch Frank <frankja@linux.ibm.com> Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com> Link: https://lore.kernel.org/r/20220322153204.2637400-1-scgl@linux.ibm.com Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
-rw-r--r--arch/s390/kvm/kvm-s390.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index da3dabda1a12..76ad6408cb2c 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2384,7 +2384,16 @@ static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop)
return -EINVAL;
if (mop->size > MEM_OP_MAX_SIZE)
return -E2BIG;
- if (kvm_s390_pv_is_protected(kvm))
+ /*
+ * This is technically a heuristic only, if the kvm->lock is not
+ * taken, it is not guaranteed that the vm is/remains non-protected.
+ * This is ok from a kernel perspective, wrongdoing is detected
+ * on the access, -EFAULT is returned and the vm may crash the
+ * next time it accesses the memory in question.
+ * There is no sane usecase to do switching and a memop on two
+ * different CPUs at the same time.
+ */
+ if (kvm_s390_pv_get_handle(kvm))
return -EINVAL;
if (mop->flags & KVM_S390_MEMOP_F_SKEY_PROTECTION) {
if (access_key_invalid(mop->key))