[xen staging] xen: vm_event: do not do vm_event_op for an invalid domain

[patchbot@xxxxxxx]

commit 6a884750f3b86a45ee5ffbd825c346fcbce86080
Author:     Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
AuthorDate: Tue Apr 8 09:36:38 2025 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Apr 8 09:36:38 2025 +0200

    xen: vm_event: do not do vm_event_op for an invalid domain
    
    A privileged domain can issue XEN_DOMCTL_vm_event_op with
    op->domain == DOMID_INVALID. In this case vm_event_domctl()
    function will get NULL as the first parameter and this will
    cause hypervisor panic, as it tries to derefer this pointer.
    
    Fix the issue by checking if valid domain is passed in.
    
    Fixes: 48b84249459f ("xen/vm-event: Drop unused u_domctl parameter from 
vm_event_domctl()")
    Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
    Acked-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
---
 xen/common/vm_event.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/xen/common/vm_event.c b/xen/common/vm_event.c
index fbf1aa0848..1666ff615f 100644
--- a/xen/common/vm_event.c
+++ b/xen/common/vm_event.c
@@ -600,6 +600,10 @@ int vm_event_domctl(struct domain *d, struct 
xen_domctl_vm_event_op *vec)
         return 0;
     }
 
+    /* All other subops need to target a real domain. */
+    if ( unlikely(d == NULL) )
+        return -ESRCH;
+
     rc = xsm_vm_event_control(XSM_PRIV, d, vec->mode, vec->op);
     if ( rc )
         return rc;
--
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