VT-d: Fix "else" vs "#endif" misplacement

In domain_pgd_maddr() the "#endif" is misplaced with respect to "else".  This
generates incorrect logic when CONFIG_HVM is compiled out, as the "else" body
is executed unconditionally.

Rework the logic to use IS_ENABLED() instead of explicit #ifdef-ary, as it's
clearer to follow.  This in turn involves adjusting p2m_get_pagetable() to
compile when CONFIG_HVM is disabled.

This is XSA-450 / CVE-2023-46840.

Fixes: 033ff90aa9c1 ("x86/P2M: p2m_{alloc,free}_ptp() and p2m_alloc_table() are HVM-only")
Reported-by: Teddy Astie <teddy.astie@vates.tech>
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
master commit: cc6ba68edf6dcd18c3865e7d7c0f1ed822796426
master date: 2024-01-30 14:29:15 +0100

diff --git a/xen/arch/x86/include/asm/p2m.h b/xen/arch/x86/include/asm/p2m.h
index cd43d8621ad25ca2a379f775fdfde3178fe7183f..4f691533d53f12740b9c7a009d022b6610eac263 100644 (file)
--- a/xen/arch/x86/include/asm/p2m.h
+++ b/xen/arch/x86/include/asm/p2m.h
@@ -447,7 +447,14 @@ static inline bool_t p2m_is_altp2m(const struct p2m_domain *p2m)
     return p2m->p2m_class == p2m_alternate;
 }
 
-#define p2m_get_pagetable(p2m)  ((p2m)->phys_table)
+#ifdef CONFIG_HVM
+static inline pagetable_t p2m_get_pagetable(const struct p2m_domain *p2m)
+{
+    return p2m->phys_table;
+}
+#else
+pagetable_t p2m_get_pagetable(const struct p2m_domain *p2m);
+#endif
 
 /*
  * Ensure any deferred p2m TLB flush has been completed on all VCPUs.

diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c
index b4c11a6b4826e244b2d084d05d6361e267633f53..908b3ba6eeff2c624f53406d3143ee1dcbba8eab 100644 (file)
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -441,15 +441,13 @@ static paddr_t domain_pgd_maddr(struct domain *d, paddr_t pgd_maddr,
 
     if ( pgd_maddr )
         /* nothing */;
-#ifdef CONFIG_HVM
-    else if ( iommu_use_hap_pt(d) )
+    else if ( IS_ENABLED(CONFIG_HVM) && iommu_use_hap_pt(d) )
     {
         pagetable_t pgt = p2m_get_pagetable(p2m_get_hostp2m(d));
 
         pgd_maddr = pagetable_get_paddr(pgt);
     }
     else
-#endif
     {
         if ( !hd->arch.vtd.pgd_maddr )
         {