[PATCH v4 3/4] KVM: s390: avoid kvm_s390_handle_pv() error overwrite

[Suren Baghdasaryan]

If kvm_s390_handle_pv() call fails its error code gets recorded but
execution proceeds as if the call was successful. If the next call to
copy_to_user() fails then the original error is overwritten.
The follow-up patch adds fatal signal checks during VMA walk, which
makes it possible for kvm_s390_handle_pv() to return EINTR error.
Without this fix any error including EINTR can be overwritten and
original error will be lost.

Change error handling for kvm_s390_handle_pv() to alter normal flow
once failure happens. This is consistent with how kvm_arch_vm_ioctl
handles errors for other ioctl commands.

Signed-off-by: Suren Baghdasaryan <surenb at google.com>
---
 arch/s390/kvm/kvm-s390.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 3eb60aa932ec..ddad08c0926f 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2947,6 +2947,8 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
 		}
 		/* must be called without kvm->lock */
 		r = kvm_s390_handle_pv(kvm, &args);
+		if (r)
+			break;
 		if (copy_to_user(argp, &args, sizeof(args))) {
 			r = -EFAULT;
 			break;
-- 
2.53.0.1018.g2bb0e51243-goog