[xen master] domctl: handle XEN_DOMCTL_io{mem,port}_permission without acquiring domctl lock

[patchbot@xxxxxxx]

commit 9f54e10bf3ab02c8d5dc3253d85c9b3258d1fc88
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Jun 4 20:20:44 2026 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Jun 9 12:45:56 2026 +0100

    domctl: handle XEN_DOMCTL_io{mem,port}_permission without acquiring domctl 
lock
    
    With dedicated locking added, the domctl lock isn't required here anymore.
    As the I/O port handling is in arch-specific code (x86 only), no code is
    being moved, but the 2nd invocation of arch_do_domctl() is re-used. Move
    the re-purposed dedicated XSM checks as early as possible.
    
    This is part of XSA-492.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Acked-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
---
 xen/arch/x86/domctl.c   | 13 ++++++++----
 xen/common/domctl.c     | 54 ++++++++++++++++++++++++++-----------------------
 xen/include/xsm/dummy.h |  6 ++++--
 xen/xsm/flask/hooks.c   |  4 ++--
 4 files changed, 44 insertions(+), 33 deletions(-)

diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
index 66c6bdf0a3..18c19c4b63 100644
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -237,12 +237,17 @@ long arch_do_domctl(
         unsigned int np = domctl->u.ioport_permission.nr_ports;
         int allow = domctl->u.ioport_permission.allow_access;
 
+        ret = -EINVAL;
+        if ( (fp + np) <= fp || (fp + np) > MAX_IOPORTS )
+            break;
+
+        ret = xsm_ioport_permission(XSM_PRIV, d, fp, fp + np - 1, allow);
+        if ( ret )
+            break;
+
         iocaps_double_lock(d, true);
 
-        if ( (fp + np) <= fp || (fp + np) > MAX_IOPORTS )
-            ret = -EINVAL;
-        else if ( !ioports_access_permitted(currd, fp, fp + np - 1) ||
-                  xsm_ioport_permission(XSM_HOOK, d, fp, fp + np - 1, allow) )
+        if ( !ioports_access_permitted(currd, fp, fp + np - 1) )
             ret = -EPERM;
         else if ( allow )
             ret = ioports_permit_access(d, fp, fp + np - 1);
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index 10460c1c57..c6c8e0440b 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -376,6 +376,34 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
             copyback = true;
         goto domctl_out_unlock_domonly;
 
+    case XEN_DOMCTL_iomem_permission:
+    {
+        unsigned long mfn = op->u.iomem_permission.first_mfn;
+        unsigned long nr_mfns = op->u.iomem_permission.nr_mfns;
+        bool allow = op->u.iomem_permission.allow_access;
+
+        ret = -EINVAL;
+        if ( (mfn + nr_mfns - 1) < mfn ) /* Wrap? */
+            goto domctl_out_unlock_domonly;
+
+        ret = xsm_iomem_permission(XSM_PRIV, d, mfn, mfn + nr_mfns - 1, allow);
+        if ( ret )
+            goto domctl_out_unlock_domonly;
+
+        iocaps_double_lock(d, true);
+
+        if ( !iomem_access_permitted(current->domain,
+                                     mfn, mfn + nr_mfns - 1) )
+            ret = -EPERM;
+        else if ( allow )
+            ret = iomem_permit_access(d, mfn, mfn + nr_mfns - 1);
+        else
+            ret = iomem_deny_access(d, mfn, mfn + nr_mfns - 1);
+
+        iocaps_double_unlock(d, true);
+        goto domctl_out_unlock_domonly;
+    }
+
     case XEN_DOMCTL_memory_mapping:
     {
         unsigned long gfn = op->u.memory_mapping.first_gfn;
@@ -436,6 +464,7 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
         goto domctl_out_unlock_domonly;
     }
 
+    case XEN_DOMCTL_ioport_permission:
     case XEN_DOMCTL_ioport_mapping:
     case XEN_DOMCTL_bind_pt_irq:
     case XEN_DOMCTL_unbind_pt_irq:
@@ -782,31 +811,6 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
     }
 #endif
 
-    case XEN_DOMCTL_iomem_permission:
-    {
-        unsigned long mfn = op->u.iomem_permission.first_mfn;
-        unsigned long nr_mfns = op->u.iomem_permission.nr_mfns;
-        int allow = op->u.iomem_permission.allow_access;
-
-        ret = -EINVAL;
-        if ( (mfn + nr_mfns - 1) < mfn ) /* wrap? */
-            break;
-
-        iocaps_double_lock(d, true);
-
-        if ( !iomem_access_permitted(current->domain,
-                                     mfn, mfn + nr_mfns - 1) ||
-             xsm_iomem_permission(XSM_HOOK, d, mfn, mfn + nr_mfns - 1, allow) )
-            ret = -EPERM;
-        else if ( allow )
-            ret = iomem_permit_access(d, mfn, mfn + nr_mfns - 1);
-        else
-            ret = iomem_deny_access(d, mfn, mfn + nr_mfns - 1);
-
-        iocaps_double_unlock(d, true);
-        break;
-    }
-
     case XEN_DOMCTL_settimeoffset:
         domain_set_time_offset(d, op->u.settimeoffset.time_offset_seconds);
         break;
diff --git a/xen/include/xsm/dummy.h b/xen/include/xsm/dummy.h
index 2ab2f5fc52..d3d2a29ae4 100644
--- a/xen/include/xsm/dummy.h
+++ b/xen/include/xsm/dummy.h
@@ -170,7 +170,9 @@ static XSM_INLINE int cf_check xsm_domctl(
     case XEN_DOMCTL_bind_pt_irq:
     case XEN_DOMCTL_getdomaininfo:
     case XEN_DOMCTL_get_domain_state:
+    case XEN_DOMCTL_iomem_permission:
     case XEN_DOMCTL_ioport_mapping:
+    case XEN_DOMCTL_ioport_permission:
     case XEN_DOMCTL_memory_mapping:
     case XEN_DOMCTL_unbind_pt_irq:
         ASSERT_UNREACHABLE();
@@ -560,7 +562,7 @@ static XSM_INLINE int cf_check xsm_irq_permission(
 static XSM_INLINE int cf_check xsm_iomem_permission(
     XSM_DEFAULT_ARG struct domain *d, uint64_t s, uint64_t e, uint8_t allow)
 {
-    XSM_ASSERT_ACTION(XSM_HOOK);
+    XSM_ASSERT_ACTION(XSM_PRIV);
     return xsm_default_action(action, current->domain, d);
 }
 
@@ -756,7 +758,7 @@ static XSM_INLINE int cf_check xsm_priv_mapping(
 static XSM_INLINE int cf_check xsm_ioport_permission(
     XSM_DEFAULT_ARG struct domain *d, uint32_t s, uint32_t e, uint8_t allow)
 {
-    XSM_ASSERT_ACTION(XSM_HOOK);
+    XSM_ASSERT_ACTION(XSM_PRIV);
     return xsm_default_action(action, current->domain, d);
 }
 
diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c
index 435cb8d661..3338a35c1e 100644
--- a/xen/xsm/flask/hooks.c
+++ b/xen/xsm/flask/hooks.c
@@ -653,7 +653,9 @@ static int cf_check flask_domctl(struct domain *d, unsigned 
int cmd,
     case XEN_DOMCTL_bind_pt_irq:
     case XEN_DOMCTL_getdomaininfo:
     case XEN_DOMCTL_get_domain_state:
+    case XEN_DOMCTL_iomem_permission:
     case XEN_DOMCTL_ioport_mapping:
+    case XEN_DOMCTL_ioport_permission:
     case XEN_DOMCTL_memory_mapping:
     case XEN_DOMCTL_unbind_pt_irq:
         ASSERT_UNREACHABLE();
@@ -662,14 +664,12 @@ static int cf_check flask_domctl(struct domain *d, 
unsigned int cmd,
     /* These have individual XSM hooks (common/domctl.c) */
     case XEN_DOMCTL_scheduler_op:
     case XEN_DOMCTL_irq_permission:
-    case XEN_DOMCTL_iomem_permission:
     case XEN_DOMCTL_set_target:
     case XEN_DOMCTL_vm_event_op:
 
 #ifdef CONFIG_X86
     /* These have individual XSM hooks (arch/x86/domctl.c) */
     case XEN_DOMCTL_shadow_op:
-    case XEN_DOMCTL_ioport_permission:
     case XEN_DOMCTL_gsi_permission:
 #endif
 #ifdef CONFIG_HAS_PASSTHROUGH
--
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