[PATCH] xen/kexec: return error code for unknown hypercalls

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Currently do_kexec_op_internal() will return 0 for unknown hypercalls.  Fix
this by returning -EOPNOTSUPP instead.

Fixes: d046f361dc93 ("Xen Security Modules: XSM")
Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Arguably the error code for unsupported kexec hypercalls was already wonky
before the XSM addiiton, as it would return -EINVAL.  It's however way
worse after the XSM addition, as it returns 0.
---
 xen/common/kexec.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/xen/common/kexec.c b/xen/common/kexec.c
index 84fe8c35976e..8f52c5506d4a 100644
--- a/xen/common/kexec.c
+++ b/xen/common/kexec.c
@@ -1217,9 +1217,8 @@ static int do_kexec_op_internal(unsigned long op,
                                 XEN_GUEST_HANDLE_PARAM(void) uarg,
                                 bool compat)
 {
-    int ret = -EINVAL;
+    int ret = xsm_kexec(XSM_PRIV);
 
-    ret = xsm_kexec(XSM_PRIV);
     if ( ret )
         return ret;
 
@@ -1258,6 +1257,10 @@ static int do_kexec_op_internal(unsigned long op,
     case KEXEC_CMD_kexec_status:
         ret = kexec_status(uarg);
         break;
+
+    default:
+        ret = -EOPNOTSUPP;
+        break;
     }
 
     clear_bit(KEXEC_FLAG_IN_HYPERCALL, &kexec_flags);
-- 
2.51.0