x86/HVM: drop stdvga's "lock" struct member

No state is left to protect. It being the last field, drop the struct
itself as well. Similarly for then ending up empty, drop the .complete
handler.

This is part of XSA-463 / CVE-2024-45818

Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
(cherry picked from commit b180a50326c8a2c171f37c1940a0fbbdcad4be90)

diff --git a/xen/arch/x86/hvm/stdvga.c b/xen/arch/x86/hvm/stdvga.c
index 3890d69c82c79bd2a2849cbfd2e7d55bea9b6795..3c5340ad9279d493d8e7d1ed4e09861f291ce237 100644 (file)
--- a/xen/arch/x86/hvm/stdvga.c
+++ b/xen/arch/x86/hvm/stdvga.c
@@ -69,61 +69,35 @@ static int stdvga_mem_write(const struct hvm_io_handler *handler,
 static bool_t stdvga_mem_accept(const struct hvm_io_handler *handler,
                                 const ioreq_t *p)
 {
-    struct hvm_hw_stdvga *s = &current->domain->arch.hvm.stdvga;
-
-    /*
-     * The range check must be done without taking the lock, to avoid
-     * deadlock when hvm_mmio_internal() is called from
-     * hvm_copy_to/from_guest_phys() in hvm_process_io_intercept().
-     */
     if ( (ioreq_mmio_first_byte(p) < VGA_MEM_BASE) ||
          (ioreq_mmio_last_byte(p) >= (VGA_MEM_BASE + VGA_MEM_SIZE)) )
         return 0;
 
-    spin_lock(&s->lock);
-
     if ( p->dir != IOREQ_WRITE || p->data_is_ptr || p->count != 1 )
     {
         /*
          * Only accept single direct writes, as that's the only thing we can
          * accelerate using buffered ioreq handling.
          */
-        goto reject;
+        return false;
     }
 
-    /* s->lock intentionally held */
-    return 1;
-
- reject:
-    spin_unlock(&s->lock);
-    return 0;
-}
-
-static void stdvga_mem_complete(const struct hvm_io_handler *handler)
-{
-    struct hvm_hw_stdvga *s = &current->domain->arch.hvm.stdvga;
-
-    spin_unlock(&s->lock);
+    return true;
 }
 
 static const struct hvm_io_ops stdvga_mem_ops = {
     .accept = stdvga_mem_accept,
     .read = stdvga_mem_read,
     .write = stdvga_mem_write,
-    .complete = stdvga_mem_complete
 };
 
 void stdvga_init(struct domain *d)
 {
-    struct hvm_hw_stdvga *s = &d->arch.hvm.stdvga;
     struct hvm_io_handler *handler;
 
     if ( !has_vvga(d) )
         return;
 
-    memset(s, 0, sizeof(*s));
-    spin_lock_init(&s->lock);
-    
     /* VGA memory */
     handler = hvm_next_io_handler(d);
     if ( handler )

diff --git a/xen/include/asm-x86/hvm/domain.h b/xen/include/asm-x86/hvm/domain.h
index 698455444ea85b691126c3e8a31c08bbd48acb25..1e5d7db6ed094551c249db56c27f8bc7d57add12 100644 (file)
--- a/xen/include/asm-x86/hvm/domain.h
+++ b/xen/include/asm-x86/hvm/domain.h
@@ -83,7 +83,6 @@ struct hvm_domain {
     struct hvm_hw_vpic     vpic[2]; /* 0=master; 1=slave */
     struct hvm_vioapic    **vioapic;
     unsigned int           nr_vioapics;
-    struct hvm_hw_stdvga   stdvga;
 
     /*
      * hvm_hw_pmtimer is a publicly-visible name. We will defer renaming

diff --git a/xen/include/asm-x86/hvm/io.h b/xen/include/asm-x86/hvm/io.h
index 2f5bfeccae390250208f9fb7b6acf7f5d2c15a45..784bd0c83f2fd1594af162dba35749f4590a1b3f 100644 (file)
--- a/xen/include/asm-x86/hvm/io.h
+++ b/xen/include/asm-x86/hvm/io.h
@@ -121,10 +121,6 @@ struct vpci_arch_msix_entry {
     int pirq;
 };
 
-struct hvm_hw_stdvga {
-    spinlock_t lock;
-};
-
 void stdvga_init(struct domain *d);
 
 extern void hvm_dpci_msi_eoi(struct domain *d, int vector);