sysctl/XSM: drop .readconsole() hook

Integrate the checking with xsm_sysctl(), now that it has the full op
struct passed. As a positive side effect, permissions are then checked at
the same early point with and without Flask.

This is part of CVE-2026-62426 / XSA-499.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-By: Daniel P. Smith <dpsmith@apertussolutions.com>
(cherry picked from commit 4b249cba4b)

xen/common/sysctl.c

@@ -59,10 +59,6 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xen_sysctl_t) u_sysctl)
     switch ( op->cmd )
     {
     case XEN_SYSCTL_readconsole:
-        ret = xsm_readconsole(XSM_HOOK, op->u.readconsole.clear);
-        if ( ret )
-            break;
-
         ret = read_console_ring(&op->u.readconsole);
         break;
 

xen/include/xsm/dummy.h

@@ -179,12 +179,6 @@ static XSM_INLINE int cf_check xsm_sysctl(
     return xsm_default_action(action, current->domain, NULL);
 }
 
-static XSM_INLINE int cf_check xsm_readconsole(XSM_DEFAULT_ARG uint32_t clear)
-{
-    XSM_ASSERT_ACTION(XSM_HOOK);
-    return xsm_default_action(action, current->domain, NULL);
-}
-
 static XSM_INLINE int cf_check xsm_alloc_security_domain(struct domain *d)
 {
     return 0;

xen/include/xsm/xsm.h

@@ -60,7 +60,6 @@ struct xsm_ops {
     int (*set_target)(struct domain *d, struct domain *e);
     int (*domctl)(struct domain *d, struct xen_domctl *op);
     int (*sysctl)(const struct xen_sysctl *op);
-    int (*readconsole)(uint32_t clear);
 
     int (*evtchn_unbound)(struct domain *d, struct evtchn *chn, domid_t id2);
     int (*evtchn_interdomain)(struct domain *d1, struct evtchn *chn1,
@@ -238,11 +237,6 @@ static inline int xsm_sysctl(xsm_default_t def, const struct xen_sysctl *op)
     return alternative_call(xsm_ops.sysctl, op);
 }
 
-static inline int xsm_readconsole(xsm_default_t def, uint32_t clear)
-{
-    return alternative_call(xsm_ops.readconsole, clear);
-}
-
 static inline int xsm_evtchn_unbound(
     xsm_default_t def, struct domain *d1, struct evtchn *chn, domid_t id2)
 {

xen/xsm/dummy.c

@@ -21,7 +21,6 @@ static const struct xsm_ops __initconst_cf_clobber dummy_ops = {
     .set_target                    = xsm_set_target,
     .domctl                        = xsm_domctl,
     .sysctl                        = xsm_sysctl,
-    .readconsole                   = xsm_readconsole,
 
     .evtchn_unbound                = xsm_evtchn_unbound,
     .evtchn_interdomain            = xsm_evtchn_interdomain,

xen/xsm/flask/hooks.c

@@ -900,13 +900,18 @@ static int cf_check flask_sysctl(const struct xen_sysctl *op)
     switch ( op->cmd )
     {
     /* These have individual XSM hooks */
-    case XEN_SYSCTL_readconsole:
     case XEN_SYSCTL_page_offline_op:
 #ifdef CONFIG_X86
     case XEN_SYSCTL_cpu_hotplug:
 #endif
         return 0;
 
+    case XEN_SYSCTL_readconsole:
+        return domain_has_xen(current->domain,
+                              XEN__READCONSOLE |
+                              (op->u.readconsole.clear ? XEN__CLEARCONSOLE
+                                                       : 0));
+
     case XEN_SYSCTL_tbuf_op:
         return domain_has_xen(current->domain, XEN__TBUFCONTROL);
 
@@ -977,16 +982,6 @@ static int cf_check flask_sysctl(const struct xen_sysctl *op)
     }
 }
 
-static int cf_check flask_readconsole(uint32_t clear)
-{
-    uint32_t perms = XEN__READCONSOLE;
-
-    if ( clear )
-        perms |= XEN__CLEARCONSOLE;
-
-    return domain_has_xen(current->domain, perms);
-}
-
 static inline uint32_t resource_to_perm(uint8_t access)
 {
     if ( access )
@@ -1912,7 +1907,6 @@ static const struct xsm_ops __initconst_cf_clobber flask_ops = {
     .set_target = flask_set_target,
     .domctl = flask_domctl,
     .sysctl = flask_sysctl,
-    .readconsole = flask_readconsole,
 
     .evtchn_unbound = flask_evtchn_unbound,
     .evtchn_interdomain = flask_evtchn_interdomain,