[xen stable-4.21] domctl: protect locking for get_domain_state

[patchbot@xxxxxxx]

commit e772f8d428bd7f2c094df6704ec392f949f55e10
Author:     Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
AuthorDate: Thu Jun 4 21:37:32 2026 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Thu Jun 4 21:38:04 2026 +0100

    domctl: protect locking for get_domain_state
    
    When DOMID_INVALID is passed, the dom exec handler lock is being taken
    without any check that the domain is even allowed to take the lock. This
    allows for an unauthorized domain to DoS the get_domain_state domctl op.
    Move to consider the op effectively being called against the hypervisor.
    Thus it is the target of the call being invoked to identify the last
    domain with a state change. The subsequent check of whether the source
    domain is allowed the state of the last domain to change state is still
    relevant.
    
    This is part of XSA-492.
    
    Signed-off-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    (cherry picked from commit 5154fdda1124ae76e6a5efc124227790d81046ab)
---
 tools/flask/policy/modules/xenstore.te |  1 +
 xen/common/domain.c                    |  6 +-----
 xen/common/domctl.c                    | 14 +++++++++++---
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/tools/flask/policy/modules/xenstore.te 
b/tools/flask/policy/modules/xenstore.te
index 776c274869..12549f5482 100644
--- a/tools/flask/policy/modules/xenstore.te
+++ b/tools/flask/policy/modules/xenstore.te
@@ -14,6 +14,7 @@ allow xenstore_t xen_t:xen writeconsole;
 # Xenstore queries domaininfo on all domains
 allow xenstore_t domain_type:domain getdomaininfo;
 allow xenstore_t domain_type:domain2 get_domain_state;
+allow xenstore_t domxen_t:domain2 get_domain_state;
 
 # As a shortcut, the following 3 rules are used instead of adding a 
domain_comms
 # rule between xenstore_t and every domain type that talks to xenstore
diff --git a/xen/common/domain.c b/xen/common/domain.c
index 88db82d187..dfeb6c7558 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -216,12 +216,8 @@ int get_domain_state(struct xen_domctl_get_domain_state 
*info, struct domain *d,
     if ( info->pad0 )
         return -EINVAL;
 
-    if ( d )
+    if ( d != dom_xen )
     {
-        rc = xsm_get_domain_state(XSM_XS_PRIV, d);
-        if ( rc )
-            return rc;
-
         set_domain_state_info(info, d);
 
         return 0;
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index 48be3ec58a..9fe097cc71 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -304,13 +304,19 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
         fallthrough;
     case XEN_DOMCTL_test_assign_device:
     case XEN_DOMCTL_vm_event_op:
-    case XEN_DOMCTL_get_domain_state:
         if ( op->domain == DOMID_INVALID )
         {
             d = NULL;
             break;
         }
         fallthrough;
+    case XEN_DOMCTL_get_domain_state:
+        if ( op->domain == DOMID_INVALID )
+        {
+            d = dom_xen;
+            break;
+        }
+        fallthrough;
     default:
         d = rcu_lock_domain_by_id(op->domain);
         if ( !d )
@@ -863,7 +869,9 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
         break;
 
     case XEN_DOMCTL_get_domain_state:
-        ret = get_domain_state(&op->u.get_domain_state, d, &op->domain);
+        ret = xsm_get_domain_state(XSM_XS_PRIV, d);
+        if ( !ret )
+            ret = get_domain_state(&op->u.get_domain_state, d, &op->domain);
         if ( !ret )
             copyback = true;
         break;
@@ -876,7 +884,7 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
     domctl_lock_release();
 
  domctl_out_unlock_domonly:
-    if ( d && d != dom_io )
+    if ( d && !is_system_domain(d) )
         rcu_unlock_domain(d);
 
     if ( copyback && __copy_to_guest(u_domctl, op, 1) )
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.21