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 1d171cb42712eb09cc8aec49abd289052e5acd22..fd38fb48002c5f54d5253f9665637b9b9896e5d7 100644 (file)
--- a/xen/arch/x86/hvm/stdvga.c
+++ b/xen/arch/x86/hvm/stdvga.c
@@ -70,61 +70,35 @@ static int cf_check stdvga_mem_write(
 static bool cf_check 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 cf_check 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/arch/x86/include/asm/hvm/domain.h b/xen/arch/x86/include/asm/hvm/domain.h
index e8e59a72bccc13db3a5bf2d901dd7082c7ee04fd..0b86329ea3786ab2a074526bc9313b9a4457cd78 100644 (file)
--- a/xen/arch/x86/include/asm/hvm/domain.h
+++ b/xen/arch/x86/include/asm/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/arch/x86/include/asm/hvm/io.h b/xen/arch/x86/include/asm/hvm/io.h
index 2f5bfeccae390250208f9fb7b6acf7f5d2c15a45..784bd0c83f2fd1594af162dba35749f4590a1b3f 100644 (file)
--- a/xen/arch/x86/include/asm/hvm/io.h
+++ b/xen/arch/x86/include/asm/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);