[RFC PATCH v4 10/10] KVM: X86: KVM_MEM_ENC_OP check if unused field (flags, error) is zero

[isaku . yamahata]

From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>

This breaks uABI as the current code doesn't check padding and sev_fd
when unused.

Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
---
Changes v3 -> v4:
- newly added
---
 arch/x86/kvm/x86.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ab36e8940f1b..1d6085af6a00 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7055,6 +7055,22 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
 			r = -EFAULT;
 			goto out;
 		}
+		/* No sub-command uses flags at the moment. */
+		if (cmd.flags) {
+			r = -EINVAL;
+			goto out;
+		}
+		if (cmd.id != KVM_SEV_LAUNCH_START &&
+		    cmd.id != KVM_SEV_RECEIVE_START && cmd.error64) {
+			r = -EINVAL;
+			goto out;
+		}
+		if ((cmd.id == KVM_SEV_LAUNCH_START ||
+		     cmd.id == KVM_SEV_RECEIVE_START) && cmd.error) {
+			r = -EINVAL;
+			goto out;
+		}
+
 		r = static_call(kvm_x86_mem_enc_ioctl)(kvm, &cmd);
 		if (copy_to_user(argp, &cmd, sizeof(cmd)))
 			r = -EFAULT;
-- 
2.25.1